BIOL 372 Exam 2 Questions
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Each of the following statements about vertical transmission of parasites is correct except for one. What is the exception?
a. Vertical transmission across generations should favor relative benignity.
b. Sexually transmitted pathogens as a rule cause benign infections when they are transmitted to neonates.
c. Vertically transmitted pathogens are expected to evolve into mutualists if mutations cause them to no longer be transmitted horizontally.
d. Vector-borne pathogens tend to be more benign in mosquito vectors when they are more vertically transmitted
e. Microsporidians tend to be more benign in mosquitoes when they are vertically transmitted.
b. Sexually transmitted pathogens as a rule cause benign infections when they are transmitted to neonates.
Which statement about "sit-and-wait" transmission is incorrect?
a. Sit-and-wait parasites are durable in the external environment and highly virulent.
b. Sit-and-wait parasites rely on the mobility of uninfected hosts to facilitate transmission.
c. Sit-and-wait pathogens cause hosts to be lethargic and thus to sit and wait for biological vectors to bite and transmit them.
d. Mortality per infection is significantly correlated with sit-and-wait transmission for human bacteria and viruses that infect the respiratory tract.
e. An evolutionary perspective on sit-and-wait transmission helps to explain why the agents of smallpox, tuberculosis, and diphtheria are severe.
c. Sit-and-wait pathogens cause hosts to be lethargic and thus to sit and wait for biological vectors to bite and transmit them.
Which of the following statements about parasites with complex life histories is incorrect?
a. The pattern of virulence in infections of predator relative to prey hosts is consistent for various groups of helminths (e.g., cestodes, nematodes, trematodes, and acanthocephalans)
b. Helminth parasites as a rule have a relatively low virulence in predator hosts
c. Helminth parasites as a rule have a relatively high virulence in prey hosts
d. Helminth parasites tend to be benign in definitive hosts, whether or not the definitive hosts acquire the parasites through predation.
e. Complex life histories of protozoal parasites may involve predator-borne transmission.
d. Helminth parasites tend to be benign in definitive hosts, whether or not the definitive hosts acquire the parasites through predation.
Each of the following findings supports the idea that transmission by biological vectors favors evolutionary increases virulence, except one.
a. Yellow fever viruses that have cycled more extensively between humans and mosquitoes are more lethal in humans.
b. Plasmodium species that have cycled extensively between humans and mosquitoes are more severe in humans than Plasmodium species that have recently been transmitted to humans from simian hosts (i.e., from monkeys or apes).
c. Transmission of viroids, such as the Cdang Cdang viroid, by insect vectors explains most of the variation in viroid virulence.
d. Pathogens transmitted between humans by biting terrestrial arthropods are more lethal than pathogens that are directly transmitted between humans.
e. Vector-borne pathogens are generally less severe when they first enter humans than after they have been transmitted among humans for many cycles.
c. Transmission of viroids, such as the Cdang Cdang viroid, by insect vectors explains most of the variation in viroid virulence.
Attendants are involved in transmission and probably in the evolution of virulence for each of the following categories of transmission except for one.
a. Waterborne diarrheal pathogens.
b. Microsporidian pathogens transmitted in water.
c. Hospital-acquired pathogens.
d. Viroids in agricultural settings.
e. Parvoviruses in kennels.
b. Microsporidian pathogens transmitted in water.
All the following routes of transmission are associated with evolution of relatively benign disease except one.
a. Vector-borne transmission of viruses in their vector hosts.
b. Transmission of microsporidians from female mosquitoes to their eggs.
c. Transmission of viruses from female mosquitoes to their eggs.
d. Transmission of microsporidians among mosquito larvae.
e. Transmission of rhinoviruses in human populations.
d. Transmission of microsporidians among mosquito larvae.
Each of the following suggests that the infrastructure of the United States protects us from severe pathogens except for one.
a. The rarity of hospital-acquired infections in the United States in recent decades.
b. The number of malaria infections arising from transmission within the United States relative to the number of imported cases.
c. The transmission of Shigella dysenteriae in Los Angeles during the early 1970s.
d. The association between screening of houses along the Tennessee River during the 1940s and malaria incidence.
e. The number of dengue infections arising from transmission within Texas relative to the number of infections that entered Texas across its border with Mexico.
a. The rarity of hospital-acquired infections in the United States in recent decades.
What is the best explanation for the evolution of high virulence of parasitoids?
a. They are not really parasites but rather are predators.
b. They have a mobile stage in their life cycle that allows their transmission to be independent of host mobility.
c. They are poorly adapted to parasitism.
d. Their hosts tend to be insects, which are inherently vulnerable to damage from parasites.
e. The death of their hosts results from the suicidal behavior of the hosts rather than the negative effects of the parasitoids.
b. They have a mobile stage in their life cycle that allows their transmission to be independent of host mobility.
What groups of organisms provide the most extensive set of host/parasite relationships confirming relatively high virulence of predator-borne parasites in prey hosts?
a. viroids
b. viruses
c. bacteria
d. helminths
e. parasitoids
d. helminths
Which of following statements offers the most reasonable explanation of Toxoplasma gondii's tendency to severely exploit rodents?
a. It is an adaptation to facilitate transmission to sandflies.
b. It is an adaptation to facilitate transmission to cats.
c. It is a side effect that occurs because rodents are not the natural host of T. gondii.
d. It is an adaptation that results from waterborne transmission of T. gondii.
e. It is an adaptation that results from vertical transmission of T. gondii in mosquitoes.
b. It is an adaptation to facilitate transmission to cats.
Which of the following statements about Toxoplasma is incorrect?
a. Toxoplasmas are protozoal parasites that are related to the protozoa that cause malaria.
b. T. gondii is transmitted by biting arthropods.
c. Cats are the definitive hosts of T. gondii.
d. T. gondii can cause birth defects and miscarriages in humans
e. T. gondii can cause dementia and death in immunocompromised adults.
b. T. gondii is transmitted by biting arthropods.
Which of the following best explains why malaria has not re-emerged in the United States?
a. Immigration control keeps people infected with Plasmodium from entering the US.
b. Our infrastructure strongly inhibits mosquito-borne transmission and therefore keeps the generation of new infections below the break-even level.
c. Our health system effectively targets and cures incoming Plasmodium infection, preventing the spread of malaria.
d. The mosquito vectors for malaria no longer exist in the US.
e. The high nutritional status of people in the US gives them resistance to Plasmodium infection.
b. Our infrastructure strongly inhibits mosquito-borne transmission and therefore keeps the generation of new infections below the break-even level.
According to the evolutionary theory of virulence, which of the following modes of transmission results in the most peaceful coexistence between host and parasite?
a. Vertical
b. vector-borne for the vertebrate host
c. sit-and-wait
d. attendant-borne
e. waterborne
a. Vertical
What is the best evolutionary explanation for the great range of virulence found among viroid diseases of plants?
a. High virulence has been favored when attendants and their tools transmit viroids, whereas low virulence has been favored when transmission occurs via seeds and pollen.
b. The variation is attributable to variation in routes of transmission in natural settings.
c. The high mutation rate of viroids is responsible for the high variation in virulence.
d. The small genome size of viroids limits the ability of viroids to regulate virulence.
e. The variation in virulence of viroids results from the broad variation in host species that the viroids infect in nature.
a. High virulence has been favored when attendants and their tools transmit viroids, whereas low virulence has been favored when transmission occurs via seeds and pollen.
Which of the following statements is an inaccurate characterization of the relationship between Shigella and waterborne transmission?
a. The most harmful species, Shigella dysenteriae, declines quickly relative to other Shigella species after protection of water supplies is first introduced.
b. Shigella flexneri predominates when improvement of water supplies has been substantial but is still incomplete.
c. The mildest species, Shigella sonnei, predominates after water supplies are completely protected.
d. The failure to control Shigella in poor countries can be important to rich countries, as evidenced by a major epidemic of Shigella dysenteriae that occurred in the United States when S. dysenteriae entered the United States from Mexico in the early 1970s and spread pervasively.
e. The association of Shigella virulence with improved water supplies occurs on local scales as well as regional scales.
d. The failure to control Shigella in poor countries can be important to rich countries, as evidenced by a major epidemic of Shigella dysenteriae that occurred in the United States when S. dysenteriae entered the United States from Mexico in the early 1970s and spread pervasively.
Which of the following interventions is not predicted by evolutionary considerations to result in evolution of reduced virulence?
a. purification of water supplies
b. making vaccines from virulence antigens
c. antibiotic treatment of ill patients when target pathogens are universally sensitive to the antibiotics
d. mosquito-proofing of houses and hospitals
e. using mild strains of the influenza virus in influenza vaccines
e. using mild strains of the influenza virus in influenza vaccines
Which of the following statements about the evolution of virulence is not consistent with current theory?
a. Fitness benefits associated with virulence arise from conversion of host resources into pathogen propagation.
b. Fitness benefits associated with virulence connect pathogen propagation with increased probability of infection per contact with susceptible individuals.
c. Fitness costs associated with virulence arise when host illness reduces the frequency of contacting susceptible individuals.
d. Fitness costs associated with virulence are influenced by modes of transmission.
e. The cost/benefit approach to virulence is an example of a valid conceptual framework that was introduced by medical experts before evolutionary biologists began making conceptual contributions to medicine.
e. The cost/benefit approach to virulence is an example of a valid conceptual framework that was introduced by medical experts before evolutionary biologists began making conceptual contributions to medicine.
Which of the following generalizations about commensalism is incorrect?
a. Given enough time, parasitism would evolve inexorably to commensalism.
b. Commensalism is defined as an interaction in which a symbiont neither harms nor benefits its host.
c. Commensalism represents a dividing line between parasitism and mutualism.
d. The category of commensalism would virtually vanish if measurements of evolutionary fitness were sufficient to calculate net fitness effects with perfect accuracy.
e. Commensalism may be more useful as an abstract concept than as a category that encompasses numerous associations.
a. Given enough time, parasitism would evolve inexorably to commensalism.
Which of the following interventions does not rank among the most successfully interventions in the history of medicine (success being measured in terms of the number of lives saved) to control infectious disease?
a. hygienic improvements that interfere with transmission
b. vaccination
c. use of antimicrobials that destroy or damage parasites inside of the host
d. application of genetic engineering and genomics to correct genetic load
e. recognition that disease can be caused by too much or too little of various noninfectious environmental factors, such as chemicals and radiation.
d. application of genetic engineering and genomics to correct genetic load
Evidence supports the idea that evolution toward benignity has played a role in control of all the following pathogens except for one.
a. Control of Corynebacterium diphtheriae using the diphtheria toxoid vaccine
b. Control of Vibrio cholerae by water purification.
c. Control of smallpox by vaccination.
d. Control of Shigella species by water purification.
e. Control of Hemophilus influenzae by a vaccine based on a virulence antigen.
c. Control of smallpox by vaccination.
Which of the following statements about cultural vectors is incorrect?
a. A cultural vector indicates the direction of a cultural change.
b. A cultural vector can include an aspect of the physical environment.
c. A cultural vector affects the evolution of virulence in a way that is analogous to the way in which a biological vector affects the evolution of virulence.
d. A cultural vector is associated with increased virulence of diarrheal pathogens.
e. A cultural vector is associated with the increased virulence of hospital-acquired pathogens.
a. A cultural vector indicates the direction of a cultural change.
Each of the following parasites are often predator-borne, except for one.
a. Toxoplasma gondii
b. Microsporidians
c. Acanthocephalan worms
d. Trematode worms
e. Cestode worms
b. Microsporidians
Which of the following statements about mosquito-proofing of dwellings is incorrect?
a. Mosquito-proofing of houses has been shown to eradicate malaria almost completely.
b. Mosquito-proofing of houses has been effective only since the introduction of pesticides, such as DDT, which are sprayed on screen doors to prevent mosquito infiltration.
c. Evolutionary theory predicts that mosquito-proofing of dwellings will favor evolution of reduced virulence of mosquito-borne pathogens such as Plasmodium falciparum.
d. Geographic variation in virulence of Plasmodium falciparum and Plasmodium vivax suggest that plasmodia have the capacity to evolve in response to mosquito-proofing of dwellings.
e. Dengue has entered the U.S. from Mexico but has failed to spread probably because of mosquito-proof dwellings.
b. Mosquito-proofing of houses has been effective only since the introduction of pesticides, such as DDT, which are sprayed on screen doors to prevent mosquito infiltration.
All the following patterns of Shigella composition during the 20th century accord with the hypothesis that water purification would favor evolution toward benignity except for one.
a. The shift from Shigella dysenteriae to Shigella flexneri in the US.
b. The shift from Shigella flexneri to Shigella sonnei in the US.
c. The continued presence of Shigella dysenteriae in Bangladesh throughout the 20th century.
d. The predominance of Shigella flexneri in Bangladesh throughout the 20th century.
e. The predominance of Shigella flexneri in the United Kingdom throughout the 20th century.
e. The predominance of Shigella flexneri in the United Kingdom throughout the 20th century.
Which of the following statements about the parasitism/mutualism continuum is incorrect?
a. Parasitism is a broad category that encompasses associations in which an individual (the parasite) lives in or on another individual (the host) and causes harm to the host.
b. Commensalism comprises about one third of the continuum and encompasses associations in which an individual lives in or on another individual without harming or helping the host individual.
c. Mutualism is a broad category that encompasses associations in which both interacting individuals benefit.
d. Virulence is a measure of the harmfulness of an infection.
e. Pathogen virulence is a measure of the inherent harmfulness of an infectious organism.
b. Commensalism comprises about one third of the continuum and encompasses associations in which an individual lives in or on another individual without harming or helping the host individual.
All the following findings support the idea that the agents of malaria can evolve levels of virulence in response to environmental influences, except one.
a. Strains of Plasmodium vivax that generate high frequencies of hypnozoites tend to be regionally restricted and produce severe illness in which people fall into a trance-like state.
b. Plasmodium falciparum infections can be unusually mild just south of the Saharan desert.
c. Plasmodium falciparum and Plasmodium vivax tend to be mild where the presence of mosquitos is highly restricted seasonally.
d. Variation necessary for evolution toward low virulence already exists in local populations where P. falciparum is damaging.
e. Plasmodium vivax strains endemic to northern latitudes (e.g., Korea) tend to be benign.
a. Strains of Plasmodium vivax that generate high frequencies of hypnozoites tend to be regionally restricted and produce severe illness in which people fall into a trance-like state.
Which of the following statements about the evolutionary control of disease is incorrect?
a. This way of controlling disease has been referred to as Virulence Management.
b. This way of controlling disease makes use of evolutionary effects of interventions that provide reductions in the frequency of infections.
c. Evolutionary control of disease focuses on causing evolutionary reductions in the harmfulness per infection.
d. Evolutionary control of disease may involve hygienic improvements, vaccination or use of antibiotics.
e. Evolutionary control of disease is now being widely incorporated into disease prevention programs as evidenced by the reliance on introduction of vector-proof housing.
e. Evolutionary control of disease is now being widely incorporated into disease prevention programs as evidenced by the reliance on introduction of vector-proof housing.
Each of the statements about virulence of malaria is justified except for one.
a. Malaria is a specific example of the tendency for vector-borne disease that evolved higher virulence than most directly transmitted pathogens.
b. When vector-borne transmission opportunities are infrequent, pathogens should evolve mechanisms to become less virulent and persist inside their host.
c. The high virulence of malaria results largely from the fact that it was recently transmitted to humans from other primate hosts such as the chimpanzee and has had insufficient time to evolve lower virulence.
d. The density of vectors dictates transmission opportunities for Plasmodium and is associated with elevated occurrence of parasitemia (parasites in the blood) in the wet seasons.
e. High virulence of Plasmodium vivax occurs in areas with more continuous mosquito-borne transmission.
c. The high virulence of malaria results largely from the fact that it was recently transmitted to humans from other primate hosts such as the chimpanzee and has had insufficient time to evolve lower virulence.
Which of the following statements about persistence of sexually transmitted pathogens is incorrect? '
a. Human papillomaviruses have evolved to be persistent by stimulating the replication of the cells they infect and by interfering with apoptosis.
b. Hepatitis B viruses have evolved to be persistent by stimulating the replication of the cells they infect and by interfering with apoptosis.
c. Human T-lymphotropic viruses (HTLVs) have evolved to be persistent by stimulating the replication of the cells they infect and by interfering with apoptosis.
d. HIV has evolved to be persistent by stimulating the replication of the cells they infect and by interfering with apoptosis.
e. Human Herpes Simplex viruses have evolved to be persistent by remains dormant in the cell bodies of neurons.
d. HIV has evolved to be persistent by stimulating the replication of the cells they infect and by interfering with apoptosis.
Which of the following statements about immunological resistance and the evolution of virulence is incorrect?
a. Vaccination might favor evolution of increased virulence if vaccine strains are derived from benign strains because immunity generated from such a vaccine could select against benign strains.
b. Partial immunity from vaccination might favor "aggressive" strains that can break through the resistance especially in populations where natural resistance is low
c. Extremely high virulence in previously unexposed human populations (such as higher mortality of smallpox and measles in Native Americans upon first contact relative to Europeans) supports the idea highly levels of resistance can favor high levels of pathogen virulence.
d. Where pathogens have been long present, the strong immunological resistance generated by infections may favor "aggressive" strains to a much greater extent than vaccination.
e. Vaccination will as a rule favor increased virulence of the target organisms.
e. Vaccination will as a rule favor increased virulence of the target organisms.
Which of the following explanations about Toxoplasma gondii infections is incorrect?
a. In its natural cycle of transmission, Toxoplasma gondii is transmitted from rodents to cats by predation.
b. The best rule of thumb for controlling antimicrobial resistance in human T. gondii infections would be to use the best available anti-toxoplasmal drug in cats to prevent transmission to humans.
c. Toxoplasma gondii infects humans but is not transmitted from adult human to adult human
d. Restricting the use of certain anti-toxoplasmal antimicrobials to humans would help control the evolution of resistance to those antimicrobials in Toxoplasma gondii.
e. Prevention of T. gondii infection in humans would likely reduce the incidence of dementia, miscarriages, and birth defects.
b. The best rule of thumb for controlling antimicrobial resistance in human T. gondii infections would be to use the best available anti-toxoplasmal drug in cats to prevent transmission to humans.
Which of the following statements about antibiotic resistance is incorrect?
a. Staphylococcus aureus began evolving resistance to methicillin within a few years after methicillin was introduced.
b. If antibiotic resistance genes are present in a small percentage of S.aureus isolates in a hospital setting, extensive antibiotic use of antibiotics can lead to resistance in most isolates within a matter of weeks.
c. Although antibiotic resistance tends to evolve in hospital settings, hospitals are isolated from each other; transfer of resistant strains between hospitals is therefore negligible.
d. Resistance to vancomycin evolved gradually decades after it was introduced because it is a last resort antibiotic and therefore is used relatively infrequently.
e. Resistance of Pseudomonas aeruginosa to fluoroquinolones increased only gradually probably because P. aeruginosa is not readily transmissible from person to person.
c. Although antibiotic resistance tends to evolve in hospital settings, hospitals are isolated from each other; transfer of resistant strains between hospitals is therefore negligible.
Each of the following statements about antibiotic resistance is correct except for one.
a. Cystic fibrosus is now readily controlled by antibiotic treatment because Pseudomonas aeruginosa, which is a major cause of damage in cystic fibrosus patients, has not been able to evolve resistance to fluoroquinolone antibiotics.
b. The selection pressure favoring increases in antibiotic resistance are particularly great in hospitals.
c. Historically, there has been a long lag between the introduction of vancomycin and the evolution of resistance to this drug probably because vancomycin was used less than other antibiotics because of damaging side effects.
d. The evolution of resistance to Enterococcus worried epidemiologists because the genes for this resistance can be transferred to Staphylococcus aureus.
e. Methicillin resistant Staphylococcus aureus (MRSA) is a big problem because it has evolved resistance to virtually all the antibiotics that had previously been effective against Staphylococcus.
a. Cystic fibrosus is now readily controlled by antibiotic treatment because Pseudomonas aeruginosa, which is a major cause of damage in cystic fibrosus patients, has not been able to evolve resistance to fluoroquinolone antibiotics.
Each of the following statements is a valid caveat about the evolution of antibiotic resistance except for one.
a. The intermixing of populations can increase the speed with which evolution of antibiotic resistance evolves.
b. The development of antibiotic resistance may depend on the extent to which people within the population have different antibiotic exposures (e.g., people in hospitals or outside of hospitals).
c. The evolution of antibiotic resistance is influenced by the extent to which antibiotic resistant strains can be transmitted between hosts relative to antibiotic sensitive strains.
d. Administration of antibiotics to a host can favor antibiotic resistance not only in the targeted organism but also in other organisms, which can then spread the resistance among different species of bacteria by transfer of plasmids.
e. The evolution of antibiotic resistance would not be a problem if patients always took the full regimen of antibiotics prescribed by their physicians.
e. The evolution of antibiotic resistance would not be a problem if patients always took the full regimen of antibiotics prescribed by their physicians.
Which of the following is not an aspect of the biological problem of antibiotic resistance in Staphylococcus?
a. Within the hospital environment, antibiotic resistance of Staphylococcus aureus can evolve from presence in a small minority of isolates to a majority within two weeks of prophylactic antibiotic treatment
b. One aspect of the problem is that antibiotic use in hospitals is high and travel between hospitals generates very large population of pathogens that can respond to this selective pressure.
c. Transport of antibiotic-resistant Staphylococcus aureus between hospitals has been documented, along with spread among patients in the affected hospitals.
d. Control of Staphylococcus antibiotic resistance will become very difficult if it acquires resistance to vancomycin, although this has not yet happened.
e. Enterococcus has acquired resistance to vancomycin, and interspecific transfer of resistance genes between Enterococcous and Staphylococcus is possible.
d. Control of Staphylococcus antibiotic resistance will become very difficult if it acquires resistance to vancomycin, although this has not yet happened.
Which of the following is not an aspect of the sociological problem of antibiotic resistance?
a. Antibiotic resistance tends to evolve in people in lower socioeconomic strata because they see physicians less frequently.
b. Antibiotic usage is often good for the patient and the physician over the short term but bad for the society over the long term, because of the generation of antibiotic resistance.
c. Curtailing inappropriate use of antibiotics will not eliminate the selective pressure favoring antibiotic resistance.
d. If antibiotic resistant variants are not yet in the patient population, patients who do not take the full regimen of antibiotics may foster the ability of pathogens to evolve antibiotic resistance gradually from low to high levels.
e. If fully antibiotic-resistant variants are already in the patient population, taking the full regimen of antibiotics may increase the rate at which evolve antibiotic resistance spreads through the population.
a. Antibiotic resistance tends to evolve in people in lower socioeconomic strata because they see physicians less frequently.
Each of the following actions should in principle suppress the evolution of antibiotic resistance except for one.
a. Restricting the antibiotic in question to dead-end infections.
b. Restricting the use of antibiotics to the infections against which the antibiotic is effective.
c. Favoring the evolution of reduced virulence by protecting against water-borne transmission.
d. Prophylactic use of antibiotics in hospital wards.
e. Favoring the evolution of reduced virulence by using virulence antigen vaccines.
d. Prophylactic use of antibiotics in hospital wards.
Which of the following generalizations is not consistent with the characteristics of the cholera strains isolated from the epidemic in Latin America during the 1990s?
a. V. cholerae evolved to be more toxigenic and less sensitive to tetracycline in Ecuador where protection of water supplies was poor.
b. V. cholerae evolved to be less toxigenic and remained sensitive to tetracycline in Chile where water supplies tend to be well protected.
c. As in Uganda, resistance to tetracycline evolved rapidly throughout Latin America, necessitating a switch to second line antibiotics.
d. The toxigenicity of V. cholerae was positively associated with the degree of antibiotic resistance in Guatemala.
e. The results suggest that protection of water supplies can favor evolution of reduced virulence and thereby suppress the evolution of antibiotic resistance.
c. As in Uganda, resistance to tetracycline evolved rapidly throughout Latin America, necessitating a switch to second line antibiotics.
Which of the following statements about virulence and transmission is incorrect?
a. The virulence and transmissibility of malaria make it a dangerous threat for emergence in the United States.
b. Epidemiological analysis of dengue transmission in Texas suggests that it is unlikely to emerge pervasively in the US.
c. The virulence and transmissibility of the smallpox virus make it a dangerous threat for emergence in the United States but a vaccine that has already been widely used could negate this threat.
d. Epidemiological analysis of s.d. transmission in Los Angeles suggests that this bacterium is unlikely to emerge pervasively in the US.
e. Epidemiological analyses of the influenza experience from the beginning of 1918 to the present suggest that fears of a reemergence of pandemic influenza in humans of the sort experienced during the latter half of 1918 have been grossly exaggerated.
a. The virulence and transmissibility of malaria make it a dangerous threat for emergence in the United States.
Which of the following is not a valid explanation for the evolution of antibiotic resistance in hospital environments?
a. Hospital acquired infections may get treated with antibiotics more often because antibiotics are readily available.
b. Hospital acquired pathogens may get treated more often because they have evolved to be more virulent and are therefore more apparent.
c. A high rate of mutations occurs in microbes that inhabit hospital environments.
d. Patients in hospitals may have compromised defenses and are therefore more vulnerable to infection and are more likely to require antibiotic treatment.
e. Pathogens can be transmitted within and between hospitals for prolonged periods of time allowing for evolution in response to selective pressures that occur in hospitals.
c. A high rate of mutations occurs in microbes that inhabit hospital environments.
Which of the following statements is incorrect?
a. The transfer of resistance-encoding plasmids between bacterial species exacerbates the problem of antibiotic resistance.
b. Reducing the use of antibiotics would be broadly beneficial both at the population level and to the individual patient who is being treated.
c. There are pathogens for which we have few if any backup antibiotics to use if the pathogen evolves resistance the currently used antibiotics.
d. If resistant variants are already in the human population, patients taking their full regimen may facilitate the emergence of resistance in the population.
e. If the resistant variants are not already in the human population, patients taking their full regimen may retard the evolution of resistance in the population.
b. Reducing the use of antibiotics would be broadly beneficial both at the population level and to the individual patient who is being treated.
Which of the following is not a valid characterization of changes in virulence and antibiotic resistance of Vibrio cholerae in Latin America during the 1990s.
a. The toxigenicity of V. cholerae declined in Chile where water supplies were well protected.
b. The toxigenicity of V. cholerae increased in Ecuador where water supplies were not well protected.
c. In Guatemala antibiotic resistance and virulence were not correlated, perhaps because the organisms arrived there late during the 1990s.
d. Antibiotic resistance began to increase in Ecuador during the late 1990s but not in Chile.
e. Increased virulence probably favored selection for increased antibiotic resistance because infections with virulent strains were more likely to be treated.
c. In Guatemala antibiotic resistance and virulence were not correlated, perhaps because the organisms arrived there late during the 1990s.
Which of the following statements is an incorrect generalization about the strategy of dead-ending?
a. Dead-ending refers to evolutionary reductions in virulence that result from the death of infected individuals.
b. Dead-ending is a strategy that involves inhibiting the evolution of antibiotic resistance.
c. Dead-ending involves using different antibiotics depending on whether infected hosts can transmit their infections to new hosts.
d. Dead-ending is a strategy that can be used to control evolutionary responses to vaccines.
e. Toxoplasma gondii and Borrelia burgdorferi are examples of organisms for which the concept of dead-ending is applicable.
a. Dead-ending refers to evolutionary reductions in virulence that result from the death of infected individuals.
All the following are valid findings that raise dangers posed by hospital acquired infections except for one.
a. Transmission of vancomycin resistance from Enterococcous to Staphylococcus.
b. Long-distance transmission of antibiotic-resistant Staphylococcus between hospitals.
c. The discovery that spread of antibiotic resistance within human populations will be prevented whenever all patients take their full regimen of antibiotics.
d. The documentation of vancomycin resistance in multiple antibiotic resistant Staphylococcus aureus over the past two decades in U.S. hospitals
e. Penicillin resistance increasing from low to high levels within two weeks after the onset of prophylactic penicillin treatment.
c. The discovery that spread of antibiotic resistance within human populations will be prevented whenever all patients take their full regimen of antibiotics.
Each of the following statements about antibiotic resistance is true except for one.
a. The development of antibiotic resistance can depend on the extent to which a population of pathogens is present within and outside of cells.
b. If resistant variants are present in the population of microbes exposed to antibiotics, evolution of antibiotic resistance will occur more rapidly than if resistant variants are absent.
c. If populations of pathogens intermix, antibiotic resistant variants can be introduced into the population that has not been exposed to the antibiotic and can serve as a basis for rapid evolution of antibiotic resistance that population.
d. Exposure to antibiotics can cause targeted organisms to respond by entering alternative life forms that are less vulnerable to the antibiotic.
e. To avoid evolution of antibiotic resistance, it is best to use broad-spectrum antibiotics because they kill all the organisms that could contribute to antibiotic resistance.
e. To avoid evolution of antibiotic resistance, it is best to use broad-spectrum antibiotics because they kill all the organisms that could contribute to antibiotic resistance.
Which of the following statements about the evolutionary effects of interventions is incorrect?
a. Blocking of waterborne transmission is predicted to favor evolutionary reductions in virulence of multiple species of diarrheal pathogens simultaneously.
b. Vector-proofing of dwellings is predicted to favor evolutionary reductions in the virulence of multiple species of vector-borne pathogens simultaneously.
c. Blocking of attendant-borne transmission in hospitals is predicted to favor evolutionary reductions in virulence of multiple species of hospital-acquired pathogens simultaneously.
d. Having infrastructure that removes durable pathogens from sites of environmental contamination (e.g., disinfection or removal of contaminated air from rooms) is predicted to favor evolutionary reductions in virulence of multiple species of respiratory tract pathogens.
e. Vaccination with a single type of vaccine is expected to favor evolutionary reductions of multiple species of respiratory tract pathogens simultaneously.
e. Vaccination with a single type fo vaccine is expected to favor evolutionary reductions of multiple species of respiratory tract pathogens simultaneously.
Which of the following explanations about Toxoplasma gondii infections is incorrect?
a. In its natural cycle of transmission, Toxoplasma gondii is transmitted from rodents to cats by predation.
b. The best rule of thumb for controlling antimicrobial resistance in human T. gondii infections would be to use the best available anti-toxoplasmal drug in cats to prevent transmission to humans.
c. Toxoplasma gondii infects humans but is not transmitted from adult human to adult human
d. Restricting the use of particular anti-toxoplasmal antimicrobials to humans would help control the evolution of resistance to those antimicrobials in Toxoplasma gondii.
e. Prevention of T. gondii infection in humans would likely reduce the incidence of dementia, miscarriages, and birth defects.
b. The best rule of thumb for controlling antimicrobial resistance in human T. gondii infections would be to use the best available anti-toxoplasmal drug in cats to prevent transmission to humans.
All of the following statements are associated with the principle of virulence management control of antimicrobial resistance except for one. What is the exception?
a. Provisioning of uncontaminated water should favor evolutionary reductions in antimicrobial resistance of diarrheal pathogens.
b. Provisioning of vector-proof houses and hospitals should favor evolutionary reductions in antimicrobial resistance of vectorborne pathogens.
c. When target pathogens are uniformly sensitive to antibiotics, antibiotic treatment should accelerate the evolution of virulence because pathogens will respond to the suppressive effects of antibiotic treatment by increasing their exploitation of the host.
d. Virulence antigen vaccines should reduce the evolution of antibiotic resistance in target pathogens
e. Blocking attendant-borne transmission should favor reduced antibiotic resistance in hospital environments
c. When target pathogens are uniformly sensitive to antibiotics, antibiotic treatment should accelerate the evolution of virulence because pathogens will respond to the suppressive effects of antibiotic treatment by increasing their exploitation of the host.
Each of the following statements about vertical transmission of parasites is correct except for one. What is the exception?
a. Vertical transmission across generations should favor relative benignity.
b. Sexually transmitted pathogens as a rule cause benign infections when they are transmitted to neonates.
c. Vertically transmitted pathogens are expected to evolve into mutualists if mutations cause them to no longer be transmitted horizontally.
d. Vector-borne pathogens tend to be more benign in mosquito vectors when they are more vertically transmitted
e. Microsporidians tend to be more benign in mosquitoes when they are vertically transmitted.
Which statement about "sit-and-wait" transmission is incorrect?
a. Sit-and-wait parasites are durable in the external environment and highly virulent.
b. Sit-and-wait parasites rely on the mobility of uninfected hosts to facilitate transmission.
c. Sit-and-wait pathogens cause hosts to be lethargic and thus to sit and wait for biological vectors to bite and transmit them.
d. Mortality per infection is significantly correlated with sit-and-wait transmission for human bacteria and viruses that infect the respiratory tract.
e. An evolutionary perspective on sit-and-wait transmission helps to explain why the agents of smallpox, tuberculosis, and diphtheria are severe.
Which of the following statements about parasites with complex life histories is incorrect?
a. The pattern of virulence in infections of predator relative to prey hosts is consistent for various groups of helminths (e.g., cestodes, nematodes, trematodes, and acanthocephalans)
b. Helminth parasites as a rule have a relatively low virulence in predator hosts
c. Helminth parasites as a rule have a relatively high virulence in prey hosts
d. Helminth parasites tend to be benign in definitive hosts whether or not the definitive hosts acquire the parasites through predation.
e. Complex life histories of protozoal parasites may involve predator-borne transmission.
Each of the following findings supports the idea that transmission by biological vectors favors evolutionary increases virulence, except one.
a. Yellow fever viruses that have cycled more extensively between humans and mosquitoes are more lethal in humans.
b. Plasmodium species that have cycled extensively between humans and mosquitoes are more severe in humans than Plasmodium species that have recently been transmitted to humans from simian hosts (i.e., from monkeys or apes).
c. Transmission of viroids, such as the Cdang Cdang viroid, by insect vectors explains most of the variation in viroid virulence.
d. Pathogens transmitted between humans by biting terrestrial arthropods are more lethal than pathogens that are directly transmitted between humans.
e. Vector-borne pathogens are generally less severe when they first enter humans than after they have been transmitted among humans for many cycles.
Attendants are involved in transmission and probably in the evolution of virulence for each of the following categories of transmission except for one.
a. Waterborne diarrheal pathogens.
b. Microsporidian pathogens transmitted in water.
c. Hospital-acquired pathogens.
d. Viroids in agricultural settings.
e. Parvoviruses in kennels.
All the following routes of transmission are associated with evolution of relatively benign disease except one.
a. Vector-borne transmission of viruses in their vector hosts.
b. Transmission of microsporidians from female mosquitoes to their eggs.
c. Transmission of viruses from female mosquitoes to their eggs.
d. Transmission of microsporidians among mosquito larvae.
e. Transmission of rhinoviruses in human populations.
Each of the following suggests that the infrastructure of the United States protects us from severe pathogens except for one.
a. The rarity of hospital-acquired infections in the United States in recent decades.
b. The number of malaria infections arising from transmission within the United States relative to the number of imported cases.
c. The transmission of Shigella dysenteriae in Los Angeles during the early 1970s.
d. The association between screening of houses along the Tennessee River during the 1940s and malaria incidence.
e. The number of dengue infections arising from transmission within Texas relative to the number of infections that entered Texas across its border with Mexico.
What is the best explanation for the evolution of high virulence of parasitoids?
a. They are not really parasites but rather are predators.
b. They have a mobile stage in their life cycle that allows their transmission to be independent of host mobility.
c. They are poorly adapted to parasitism.
d. Their hosts tend to be insects, which are inherently vulnerable to damage from parasites.
e. The death of their hosts results from suicidal behavior of the hosts rather than the negative effects of the parasitoids.
What groups of organisms provide the most extensive set of host/parasite relationships confirming relatively high virulence of predator-borne parasites in prey hosts?
a. viroids
b. viruses
c. bacteria
d. helminths
e. parasitoids
Which of following statements offers the most reasonable explanation of Toxoplasma gondii's tendency to severely exploit rodents?
a. It is an adaptation to facilitate transmission to sandflies.
b. It is an adaptation to facilitate transmission to cats.
c. It is a side effect that occurs because rodents are not the natural host of T. gondii.
d. It is an adaptation that results from waterborne transmission of T. gondii.
e. It is an adaptation that results from vertical transmission of T. gondii in mosquitoes.
Which of the following statements about Toxoplasma is incorrect?
a. Toxoplasmas are protozoal parasites that are related to the protozoa that cause malaria.
b. T. gondii is transmitted by biting arthropods.
c. Cats are the definitive hosts of T. gondii.
d. T. gondii can cause birth defects and miscarriages in humans
e. T. gondii can cause dementia and death in immunocompromised adults.
Which of the following best explains why malaria has not re-emerged in the United States?
a. Immigration control keeps people infected with Plasmodium from entering the US.
b. Our infrastructure strongly inhibits mosquito-borne transmission and therefore keeps the generation of new infections below the break-even level.
c. Our health system effectively targets and cures incoming Plasmodium infection, preventing the spread of malaria.
d. The mosquito vectors for malaria no longer exist in the US.
e. The high nutritional status of people in the US gives them resistance to Plasmodium infection.
According to the evolutionary theory of virulence, which of the following modes of transmission results in the most peaceful coexistence between host and parasite?
a. Vertical
b. vector-borne for the vertebrate host
c. sit-and-wait
d. attendant-borne
e. waterborne
What is the best evolutionary explanation for the great range of virulence found among viroid diseases of plants?
a. High virulence has been favored when attendants and their tools transmit viroids, whereas low virulence has been favored when transmission occurs via seeds and pollen.
b. The variation is attributable to variation in routes of transmission in natural settings.
c. The high mutation rate of viroids is responsible for the high variation in virulence.
d. The small genome size of viroids limits the ability of viroids to regulate virulence.
e. The variation in virulence of viroids results from the broad variation in host species that the viroids infect in nature.
Which of the following statements is an inaccurate characterization of the relationship between Shigella and waterborne transmission?
a. The most harmful species, Shigella dysenteriae, declines quickly relative to other Shigella species after protection of water supplies is first introduced.
b. Shigella flexneri predominates when improvement of water supplies has been substantial but is still incomplete.
c. The mildest species, Shigella sonnei, predominates after water supplies are completely protected.
d. The failure to control Shigella in poor countries can be important to rich countries, as evidenced by a major epidemic of Shigella dysenteriae that occurred in the United States when S. dysenteriae entered the United States from Mexico in the early 1970s and spread pervasively.
e. The association of Shigella virulence with improved water supplies occurs on local scales as well as regional scales.
Which of the following interventions is not predicted by evolutionary considerations to result in evolution of reduced virulence?
a. purification of water supplies
b. making vaccines from virulence antigens
c. antibiotic treatment of ill patients when target pathogens are universally sensitive to the antibiotics
d. mosquito-proofing of houses and hospitals
e. using mild strains of the influenza virus in influenza vaccines
Which of the following statements about the evolution of virulence is not consistent with current theory?
a. Fitness benefits associated with virulence arise from conversion of host resources into pathogen propagation.
b. Fitness benefits associated with virulence connect pathogen propagation with increased probability of infection per contact with susceptible individuals.
c. Fitness costs associated with virulence arise when host illness reduces the frequency of contacting susceptible individuals.
d. Fitness costs associated with virulence are influenced by modes of transmission.
e. The cost/benefit approach to virulence is an example of a valid conceptual framework that was introduced by medical experts before evolutionary biologists began making conceptual contributions to medicine.
Which of the following generalizations about commensalism is incorrect?
a. Given enough time parasitism would evolve inexorably to commensalism.
b. Commensalism is defined as an interaction in which a symbiont neither harms nor benefits its host.
c. Commensalism represents a dividing line between parasitism and mutualism.
d. The category of commensalism would virtually vanish if measurements of evolutionary fitness were sufficient to calculate net fitness effects with perfect accuracy.
e. Commensalism may be more useful as an abstract concept than as a category that encompasses numerous associations.
Which of the following interventions does not rank among the most successfully interventions in the history of medicine (success being measured in terms of the number of lives saved) to control infectious disease
a. hygienic improvements that interfere with transmission
b. vaccination
c. use of antimicrobials that destroy or damage parasites inside of the host
d. application of genetic engineering and genomics to correct genetic load
e. recognition that disease can be caused by too much or too little of various noninfectious environmental factors, such as chemicals and radiation.
Evidence supports the idea that evolution toward benignity has played a role in control of all the following pathogens except for one.
a. Control of Corynebacterium diphtheriae using the diphtheria toxoid vaccine
b. Control of Vibrio cholerae by water purification.
c. Control of smallpox by vaccination.
d. Control of Shigella species by water purification.
e. Control of Hemophilus influenzae by a vaccine based on a virulence antigen.
Which of the following statements about cultural vectors is incorrect?
a. A cultural vector indicates the direction of a cultural change.
b. A cultural vector can include an aspect of the physical environment.
c. A cultural vector affects the evolution of virulence in a way that is analogous to the way in which a biological vector affects the evolution of virulence.
d. A cultural vector is associated with increased virulence of diarrheal pathogens.
e. A cultural vector is associated with the increased virulence of hospital-acquired pathogens.
Each of the following parasites are often predator-borne, except for one.
a. Toxoplasma gondii
b. Microsporidians
c. Acanthocephalan worms
d. Trematode worms
e. Cestode worms
Which of the following statements about mosquito-proofing of dwellings is incorrect?
a. Mosquito-proofing of houses has been shown to eradicate malaria almost completely.
b. Mosquito-proofing of houses has been effective only since the introduction of pesticides, such as DDT, which are sprayed on screen doors to prevent mosquito infiltration.
c. Evolutionary theory predicts that mosquito-proofing of dwellings will favor evolution of reduced virulence of mosquito-borne pathogens such as Plasmodium falciparum.
d. Geographic variation in virulence of Plasmodium falciparum and Plasmodium vivax suggest that plasmodia have the capacity to evolve in response to mosquito-proofing of dwellings.
e. Dengue has entered the U.S. from Mexico but has failed to spread probably because of mosquito-proof dwellings.
All the following patterns of Shigella composition during the 20th century accord with the hypothesis that water purification would favor evolution toward benignity except for one.
a. The shift from Shigella dysenteriae to Shigella flexneri in the US.
b. The shift from Shigella flexneri to Shigella sonnei in the US
c. The continued presence of Shigella dysenteriae in Bangladesh throughout the 20th century.
d. The predominance of Shigella flexneri in Bangladesh throughout the 20th century.
e. The predominance of Shigella flexneri in the United Kingdom throughout the 20th century.
Which of the following statements about the parasitism/mutualism continuum is incorrect?
a. Parasitism is a broad category that encompasses associations in which an individual (the parasite) lives in or on another individual (the host) and causes harm to the host.
b. Commensalism comprises about one third of the continuum and encompasses associations in which an individual lives in or on another individual without harming or helping the host individual.
c. Mutualism is a broad category that encompasses associations in which both interacting individuals benefit.
d. Virulence is a measure of the harmfulness of an infection.
e. Pathogen virulence is a measure of the inherent harmfulness of an infectious organism.
All the following findings support the idea that the agents of malaria can evolve levels of virulence in response to environmental influences, except one.
a. Strains of Plasmodium vivax that generate high frequencies of hypnozoites tend to be regionally restricted and produce severe illness in which people fall into a trance-like state.
b. Plasmodium falciparum infections can be unusually mild just south of the Saharan desert.
c. Plasmodium falciparum and Plasmodium vivax tend to be mild where the presence of mosquitos is highly restricted seasonally.
d. Variation necessary for evolution toward low virulence already exists in local populations where P. falciparum is damaging.
e. Plasmodium vivax strains endemic to northern latitudes (e.g., Korea) tend to be benign.
Which of the following statements about the evolutionary control of disease is incorrect?
a. This way of controlling disease has been referred to as Virulence Management.
b. This way of controlling disease makes use of evolutionary effects of interventions that provide reductions in the frequency of infections.
c. Evolutionary control of disease focuses on causing evolutionary reductions in the harmfulness per infection.
d. Evolutionary control of disease may involve hygienic improvements, vaccination or use of antibiotics.
e. Evolutionary control of disease is now being widely incorporated into disease prevention programs as evidenced by the reliance on introduction of vector-proof housing.
Each of the statements about virulence of malaria is justified except for one.
a. Malaria is a specific example of the tendency for vector-borne disease that evolved higher virulence than most directly transmitted pathogens.
b. When vector-borne transmission opportunities are infrequent, pathogens should evolve mechanisms to become less virulent and persist inside their host.
c. The high virulence of malaria results largely from the fact that it was recently transmitted to humans from other primate hosts such as the chimpanzee and has had insufficient time to evolve lower virulence.
d. The density of vectors dictates transmission opportunities for Plasmodium and is associated with elevated occurrence of parasitemia (parasites in the blood) in the wet seasons.
e. High virulence of Plasmodium vivax occurs in areas with more continuous mosquito-borne transmission.
Which of the following statements about persistence of sexually transmitted pathogens is incorrect?
a. Human papillomaviruses have evolved to be persistent by stimulating the replication of the cells they infect and by interfering with apoptosis.
b. Hepatitis B viruses have evolved to be persistent by stimulating the replication of the cells they infect and by interfering with apoptosis.
c. Human T-lymphotropic viruses (HTLVs) have evolved to be persistent by stimulating the replication of the cells they infect and by interfering with apoptosis.
d. HIV has evolved to be persistent by stimulating the replication of the cells they infect and by interfering with apoptosis.
e. Human Herpes Simplex viruses have evolved to be persistent by remains dormant in the cell bodies of neurons.
Which of the following statements about immunological resistance and the evolution of virulence is incorrect?
a. Vaccination might favor evolution of increased virulence if vaccine strains are derived from benign strains because immunity generated from such a vaccine could select against benign strains.
b. Partial immunity from vaccination might favor "aggressive" strains that can break through the resistance especially in populations where natural resistance is low
c. Extremely high virulence in previously unexposed human populations (such as higher mortality of smallpox and measles in Native Americans upon first contact relative to Europeans) supports the idea highly levels of resistance can favor high levels of pathogen virulence.
d. Where pathogens have been long present, the strong immunological resistance generated by infections may favor "aggressive" strains to a much greater extent than vaccination.
e. Vaccination will as a rule favor increased virulence of the target organisms.
Which of the following explanations about Toxoplasma gondii infections is incorrect?
a. In its natural cycle of transmission, Toxoplasma gondii is transmitted from rodents to cats by predation.
b. The best rule of thumb for controlling antimicrobial resistance in human T. gondii infections would be to use the best available anti-toxoplasmal drug in cats to prevent transmission to humans.
c. Toxoplasma gondii infects humans but is not transmitted from adult human to adult human
d. Restricting the use of certain anti-toxoplasmal antimicrobials to humans would help control the evolution of resistance to those antimicrobials in Toxoplasma gondii.
e. Prevention of T. gondii infection in humans would likely reduce the incidence of dementia, miscarriages, and birth defects.
Which of the following statements about antibiotic resistance is incorrect?
a. Staphylococcus aureus began evolving resistance to methicillin within a few years after methicillin was introduced.
b. If antibiotic resistance genes are present in a small percentage of S.aureus isolates in a hospital setting, extensive antibiotic use of antibiotics can lead to resistance in most isolates within a matter of weeks.
c. Although antibiotic resistance tends to evolve in hospital settings, hospitals are isolated from each other; transfer of resistant strains between hospitals is therefore negligible.
d. Resistance to vancomycin evolved gradually decades after it was introduced because it is a last resort antibiotic and therefore is used relatively infrequently.
e. Resistance of Pseudomonas aeruginosa to fluoroquinolones increased only gradually probably because P. aeruginosa is not readily transmissible from person to person.
Each of the following statements about antibiotic resistance is correct except for one.
a. Cystic fibrosus is now readily controlled by antibiotic treatment because Pseudomonas aeruginosa, which is a major cause of damage in cystic fibrosus patients, has not been able to evolve resistance to fluoroquinolone antibiotics.
b. The selection pressure favoring increases in antibiotic resistance are particularly great in hospitals.
c. Historically, there has been a long lag between the introduction of vancomycin and the evolution of resistance to this drug probably because vancomycin was used less than other antibiotics because of damaging side effects.
d. The evolution of resistance to Enterococcus worried epidemiologists because the genes for this resistance can be transferred to Staphylococcus aureus.
e. Methicillin resistant Staphylococcus aureus (MRSA) is a big problem because it has evolved resistance to virtually all the antibiotics that had previously been effective against Staphylococcus.
Each of the following statements is a valid caveat about the evolution of antibiotic resistance except for one.
a. The intermixing of populations can increase the speed with which evolution of antibiotic resistance evolves.
b. The development of antibiotic resistance may depend on the extent to which people within the population have different antibiotic exposures (e.g., people in hospitals or outside of hospitals).
c. The evolution of antibiotic resistance is influenced by the extent to which antibiotic resistant strains can be transmitted between hosts relative to antibiotic sensitive strains.
d. Administration of antibiotics to a host can favor antibiotic resistance not only in the targeted organism but also in other organisms, which can then spread the resistance among different species of bacteria by transfer of plasmids.
e. The evolution of antibiotic resistance would not be a problem if patients always took the full regimen of antibiotics prescribed by their physicians.
e. The evolution of antibiotic resistance would not be a problem if patients always took the full regimen of antibiotics prescribed by their physicians.
Which of the following is not an aspect of the biological problem of antibiotic resistance in Staphylococcus?
a. Within the hospital environment, antibiotic resistance of Staphylococcus aureus can evolve from presence in a small minority of isolates to a majority within two weeks of prophylactic antibiotic treatment
b. One aspect of the problem is that antibiotic use in hospitals is high and travel between hospitals generates very large population of pathogens that can respond to this selective pressure.
c. Transport of antibiotic-resistant Staphylococcus aureus between hospitals has been documented, along with spread among patients in the affected hospitals.
d. Control of Staphylococcus antibiotic resistance will become very difficult if it acquires resistance to vancomycin, although this has not yet happened.
e. Enterococcus has acquired resistance to vancomycin, and interspecific transfer of resistance genes between Enterococcous and Staphylococcus is possible.
d. Control of Staphylococcus antibiotic resistance will become very difficult if it acquires resistance to vancomycin, although this has not yet happened.
Which of the following is not an aspect of the sociological problem of antibiotic resistance?
a. Antibiotic resistance tends to evolve in people in lower socioeconomic strata because they see physicians less frequently.
b. Antibiotic usage is often good for the patient and the physician over the short term but bad for the society over the long term, because of the generation of antibiotic resistance.
c. Curtailing inappropriate use of antibiotics will not eliminate the selective pressure favoring antibiotic resistance.
d. If antibiotic resistant variants are not yet in the patient population, patients who do not take the full regimen of antibiotics may foster the ability of pathogens to evolve antibiotic resistance gradually from low to high levels
e. If fully antibiotic-resistant variants are already in the patient population, taking the full regimen of antibiotics may increase the rate at which evolve antibiotic resistance spreads through the population.
a. Antibiotic resistance tends to evolve in people in lower socioeconomic strata because they see physicians less frequently.
Each of the following actions should in principle suppress the evolution of antibiotic resistance except for one.
a. Restricting the antibiotic in question to dead-end infections.
b. Restricting the use of antibiotics to the infections against which the antibiotic is effective.
c. Favoring the evolution of reduced virulence by protecting against water-borne transmission.
d. Prophylactic use of antibiotics in hospital wards.
e. Favoring the evolution of reduced virulence by using virulence antigen vaccines.
d. Prophylactic use of antibiotics in hospital wards.
Which of the following generalizations is not consistent with the characteristics of the cholera strains isolated from the epidemic in Latin America during the 1990s?
a. V. cholerae evolved to be more toxigenic and less sensitive to tetracycline in Ecuador where protection of water supplies was poor.
b. V. cholerae evolved to be less toxigenic and remained sensitive to tetracycline in Chile where water supplies tend to be well protected.
c. As in Uganda, resistance to tetracycline evolved rapidly throughout Latin America, necessitating a switch to second line antibiotics.
d. The toxigenicity of V. cholerae was positively associated with the degree of antibiotic resistance in Guatemala.
e. The results suggest that protection of water supplies can favor evolution of reduced virulence and thereby suppress the evolution of antibiotic resistance.
c. As in Uganda, resistance to tetracycline evolved rapidly throughout Latin America, necessitating a switch to second line antibiotics.
Which of the following statements about virulence and transmission is incorrect?
a. The virulence and transmissibility of malaria make it a dangerous threat for emergence in the United States.
b. Epidemiological analysis of dengue transmission in Texas suggests that it is unlikely to emerge pervasively in the US.
c. The virulence and transmissibility of the smallpox virus make it a dangerous threat for emergence in the United States but a vaccine that has already been widely used could negate this threat.
d. Epidemiological analysis of s.d. transmission in Los Angeles suggests that this bacterium is unlikely to emerge pervasively in the US.
e. Epidemiological analyses of the influenza experience from the beginning of 1918 to the present suggest that fears of a reemergence of pandemic influenza in humans of the sort experienced during the latter half of 1918 have been grossly exaggerated.
a. The virulence and transmissibility of malaria make it a dangerous threat for emergence in the United States.
Which of the following is not a valid explanation for the evolution of antibiotic resistance in hospital environments?
a. Hospital acquired infections may get treated with antibiotics more often because antibiotics are readily available.
b. Hospital acquired pathogens may get treated more often because they have evolved to be more virulent and are therefore more apparent.
c. A high rate of mutations occurs in microbes that inhabit hospital environments.
d. Patients in hospitals may have compromised defenses and are therefore more vulnerable to infection and are more likely to require antibiotic treatment.
e. Pathogens can be transmitted within and between hospitals for prolonged periods of time allowing for evolution in response to selective pressures that occur in hospitals.
c. A high rate of mutations occurs in microbes that inhabit hospital environments.
Which of the following statements is incorrect?
a. The transfer of resistance-encoding plasmids between bacterial species exacerbates the problem of antibiotic resistance.
b. Reducing the use of antibiotics would be broadly beneficial both at the population level and to the individual patient who is being treated.
c. There are pathogens for which we have few if any backup antibiotics to use if the pathogen evolves resistance the currently used antibiotics.
d. If resistant variants are already in the human population, patients taking their full regimen may facilitate the emergence of resistance in the population.
e. If the resistant variants are not already in the human population, patients taking their full regimen may retard the evolution of resistance in the population.
b. Reducing the use of antibiotics would be broadly beneficial both at the population level and to the individual patient who is being treated.
Which of the following is not a valid characterization of changes in virulence and antibiotic resistance of Vibrio cholerae in Latin America during the 1990s.
a. The toxigenicity of V. cholerae declined in Chile where water supplies were well protected.
b. The toxigenicity of V. cholerae increased in Ecuador where water supplies were not well protected.
c. In Guatemala antibiotic resistance and virulence were not correlated, perhaps because the organisms arrived there late during the 1990s.
d. Antibiotic resistance began to increase in Ecuador during the late 1990s but not in Chile.
e. Increased virulence probably favored selection for increased antibiotic resistance because infections with virulent strains were more likely to be treated.
c. In Guatemala antibiotic resistance and virulence were not correlated, perhaps because the organisms arrived there late during the 1990s.
Which of the following statements is an incorrect generalization about the strategy of dead-ending?
a. Dead-ending refers to evolutionary reductions in virulence that result from the death of infected individuals.
b. Dead-ending is a strategy that involves inhibiting the evolution of antibiotic resistance.
c. Dead-ending involves using different antibiotics depending on whether infected hosts can transmit their infections to new hosts.
d. Dead-ending is a strategy that can be used to control evolutionary responses to vaccines.
e. Toxoplasma gondii and Borrelia burgdorferi are examples of organisms for which the concept of dead-ending is applicable.
a. Dead-ending refers to evolutionary reductions in virulence that result from the death of infected individuals.
All the following are valid findings that raise dangers posed by hospital acquired infections except for one.
a. Transmission of vancomycin resistance from Enterococcous to Staphylococcus.
b. Long-distance transmission of antibiotic-resistant Staphylococcus between hospitals.
c. The discovery that spread of antibiotic resistance within human populations will be prevented whenever all patients take their full regimen of antibiotics.
d. The documentation of vancomycin resistance in multiple antibiotic resistant Staphylococcus aureus over the past two decades in U.S. hospitals
e. Penicillin resistance increasing from low to high levels within two weeks after the onset of prophylactic penicillin treatment.
c. The discovery that spread of antibiotic resistance within human populations will be prevented whenever all patients take their full regimen of antibiotics.
Each of the following statements about antibiotic resistance is true except for one.
a. The development of antibiotic resistance can depend on the extent to which a population of pathogens is present within and outside of cells.
b. If resistant variants are present in the population of microbes exposed to antibiotics, evolution of antibiotic resistance will occur more rapidly than if resistant variants are absent.
c. If populations of pathogens intermix, antibiotic resistant variants can be introduced into the population that has not been exposed to the antibiotic and can serve as a basis for rapid evolution of antibiotic resistance that population.
d. Exposure to antibiotics can cause targeted organisms to respond by entering alternative life forms that are less vulnerable to the antibiotic.
e. To avoid evolution of antibiotic resistance, it is best to use broad-spectrum antibiotics because they kill all the organisms that could contribute to antibiotic resistance.
e. To avoid evolution of antibiotic resistance, it is best to use broad-spectrum antibiotics because they kill all the organisms that could contribute to antibiotic resistance.
Which of the following statements about needle-borne Plasmodium is incorrect?
a. Intentional transmission of Plasmodium has been used as therapy for syphilis
b. After being transferred by needle from human to human for over 100 consecutive transfers, Plasmodium knowlesi increased in virulence.
c. Plasmodium has not been unintentionally transmitted via needles in the United States.
d. The intentional transfer of Plasmodium during therapy has been associated with an increase in the number of parasites per mm3 of blood from about 1,000 to about 500,000.
e. Benign Plasmodium can evolve to cause lethal disease as a result of intentional needleborne transmission
c. Plasmodium has not been unintentionally transmitted via needles in the United States.
Which generalization does not apply to needle-borne pathogens?
a. They can be transmitted by donated blood.
b. They can be transmitted by illegal drug use.
c. They can be transmitted by medicinal products such as clotting factor.
d. They often are sexually transmitted as well as needle-borne.
e. They are often waterborne as well as needle-borne.
e. They are often waterborne as well as needle-borne.
Which of the following statements about needle-borne pathogens is incorrect?
a. Malaria can be both mosquito-borne and needle-borne.
b. Neisseria gonorrheae can often be needle-borne or sexually transmitted.
c. Human Immunodeficiency Virus can often be needle-borne or sexually transmitted.
d. HBV can often be needle-borne or sexually transmitted.
e. Reduction of needle-borne transmission through needle exchange programs has been associated with milder HIV infections in New York and in Europe.
b. Neisseria gonorrheae can often be needle-borne or sexually transmitted.
Needle borne transmission has not been implicated for which one of the following pathogens?
a. HIV
b. influenza virus
c. Hepatitis C virus
d. Hepatitis B virus
e. Plasmodium species
b. influenza virus
Which of the following statements about therapeutic use of malaria is incorrect?
a. Prior to the discovery of effective antibiotics, injections of Plasmodium had been used to treat syphilis.
b. A big problem with using Plasmodium therapeutically was that it evolved increased virulence as it was sequentially transferred from patient to patient.
c. A big problem with using Plasmodium therapeutically is that control of parasitemia can be difficult.
d. A big problem with using Plasmodium therapeutically was that P. falciparum was used, and it is notorious for causing severe malaria.
e. Although malaria was presumed to be effective in controlling bacterial infections as a result of the fever it caused, other symptomatic effects of Plasmodium infection raise alternative explanations for its effectiveness.
d. A big problem with using Plasmodium therapeutically was that P. falciparum was used, and it is notorious for causing severe malaria.
Which of the following does not support the hypothesis that needle-borne transmission may increase virulence?
a. Comparison of the HIV infections in Finland with those in the Netherlands
b. Faster progression to AIDS among Puerto Ricans than among Puerto Rican Americans living in New York City
c. Less virulent HIV infections where needle exchange programs have been enacted.
d. Increased rates of evolutionary change of HTLV-2 in drug users relative to non drug using native Americans.
e. Lower HIV virulence in Senegal than in the Ivory Coast.
e. Lower HIV virulence in Senegal than in the Ivory Coast.
Which of the following statements about HTLV-2 infections is incorrect?
a. The distribution of HTLV-II indicates that it has been endemic in native Americans from the time of their arrival in North America over 10,000 years ago.
b. Historically, HTLV-II had been more benign than HTLV-I, presumably because HTLV-II had been transmitted in societies with infrequent opportunities of transmission, which would have favored mild variants.
c. HTLV-II became endemic in intravenous drug users a few decades ago.
d. Measurements of rates of genetic change indicate that HTLV-II has been replicating and evolving much more rapidly in intravenous drug users than in the historically endemic populations.
e. In non-drug-using, non-Amerindian populations, mortality is as low as among nondrug using native Americans.
E. In non-drug-using, non-Amerindian populations, mortality is as low as among nondrug using native Americans.