Microbiology Module I Study guide Chapters 1-13

1.     What is a prokaryote?

Simple, single-celled organism that lacks a nucleus and membrane bound organelles

2.     What substance forms many bacterial walls and consists of glycosaminoglycan chains interlinked with short peptides?

Peptidoglycan

3.     What structure does penicillin target to disrupt the integrity of the bacterial cell wall? Attach the diagram from slide #10.

Peptide cross-links

4.     What is a bacterial chromosome?

Single, large, circular, double-stranded DNA molecule that contains all the genetic information required by a cell

            -located in the nucleoid

5.     What is a plasmid?

Small, circular, double-stranded DNA; not essential to growth or metabolism; duplicated and passed down to offspring

            -located in the nucleoid

6.     Briefly describe transcription and translation synthesis and explain why they can occur simultaneously in the prokaryotic cell.

Transcription: synthesis of mRNA from DNA

Translation: synthesis of proteins from mRNA

-the two process are couple allowing the cell to quickly make protein

-this happens because the cell lacks a membrane bound nucleus; all components needed in the cytoplasm

7.     Which bacterial genres produce endospores? Which bacteria is known to cause outbreaks of diarrhea in hospitals and nursing homes? Will bleach-free disinfectants kill this bacterium?

-Bacillus and Clostridium

-C. diff

-resistant to bleach-free disinfectants

8.     Which type of bacteria has a thick layer of peptidoglycan that forms a single layer around the cell? During a gram stain, what color will this type of bacteria appear under a microscope? Why? 

Gram +; purple bc it retains the crystal violet stain

9.     Describe the steps involved in performing a gram stain. Which step is the most critical and why?

Flood slide with crystal violet x10 sec then rinse  flood with Gram’s iodine x 10 sec then rinse  decolorize with 95% ethanol until thinnest parts are colorless then rinse  flood with safranin (pink) x10 sec then rinse air dry or blot with absorbent paper. The third step is the most important because it is the most affected by technical variations in timing and reagents

10.  When viewed under a microscope, which gram-positive bacteria appear as cocci in clusters “bunches of grapes”?

Staphylococcaceae

11.  When viewed under a microscope, which gram-positive bacteria appear as cocci in pairs or chains?

Streptococcus

12.  There has been a recent outbreak of listeria that has been linked to contaminated deli meat. Describe how this bacterium would look after a gram stain when viewed through a microscope. (Color and shape) Does this bacterium produce spores?

Gram +, purple, linked rods, non-sporeforming

13.  Define pleomorphism. Why is pleomorphism extreme in the Mycoplasma genus of bacteria?

Present in different sizes and shapes due to variations in cell wall

14.  List the 6 I’s of culturing microbes and the purpose of each.

Inoculation: introduction of sample into a container of sterile media

Incubation: provides conditions for optimal growth

Isolation: getting a pure culture of the microbe

Inspection: looking at colonies and microscopic characteristics

Information gathering: biochemical, immunologic, and genetic testing

Identification: assigning a specific name to the microbe

15.  What factors affect microbial growth?

Nutrients, temperature, pH and presence of water, atmospheric gases (O2, CO2, N2)

16.  Describe synthetic, non-synthetic, general purpose, enriched, selective, and differential media.

Synthetic: contains pure organic and inorganic compounds in an exact chemical formula

Non-synthetic: contains at least one ingredient that is not chemically definable: organic extracts

General purpose: grows on a broad range of microbes, usually non-synthetic, nutrient agar and broth, peptone water, etc

Enriched: contains complex organic substances such as blood, serum, hemoglobin, or special growth factors required by fastidious microbes

Selective: contains one or more agents that inhibit growth of some microbes and encourage growth of the desired microbes

Differential: allows growth of several types of microbes and displays visible difference among desired and undesired microbes

17.  Which specific medium would be best to isolate pathogenic Staphylococci?

Selective

18.  Why is the growth curve in a bacterial culture closed? What is the average period it takes to complete this curve?

Nutrients and space are finite: no mechanism for the removal of waste products

Entire curve is exhibited over a period of 4 days

19.  List and describe the four phases in the microbial growth curve.

Lag: “flat” period of adjustment, enlargement, and synthesis of DNA, enzymes, ribosomes; little growth

Exponential Growth (Log): period of maximum growth will continue if cells have adequate nutrients and a favorable environment

Stationary: rate of cell growth = rate of cell death; caused by depleted nutrients and O2, excretion of organic acids and pollutants

Death: as limiting factors intensify, cells die exponentially in their own wastes

20.  Which gram-positive bacteria stain like gram-negative bacteria? Why?

Actinomyces, corynebacterium, mycobacterium, Propionibacterium due to their walls being sensitive to breakage during cell division

21.  Which bacteria respond best to acid-fast staining?

Mycobacteria

22.  Which groups of bacteria are considered obligate intracellular parasites? How are they different from non-obligate intracellular bacteria?

Rickettsia and Chlamydia: cannot survive or multiply outside of a host cell; cannot carry out metabolism on their own

23.  List the 4 main fungal divisions. Give examples of each division except for the one that does not cause human disease.

Zygomycota -bread mold

Ascomycota -penicillium, yeast, ringworm, candida albicans, black mold

Basidiomycota -Crypto Neoformans

Chytridiomycota -does not harm humans

24.   What are the two morphologies in which microscopic fungi exist?  

Yeast and Hyphae (molds)

25.  What is the difference between primary and opportunistic fungal pathogens? List examples of both.

Primary: exist in yeast and mold forms (dimorphic) -histoplasma, Blastomyces

Opportunistic: happen secondary to a weakened immune system -cryptococcus, candida

26.  Marine algae toxins can cause food poisoning. List the two examples given in the lecture and the marine life each condition is associated with.

Red tide: algae  animals  toxic

Paralytic shellfish: exposed clams  neurological symptoms

Ciguatera fish poisoning: serious intoxication -barracuda and moray eel, mahi

27.  What are the two protozoan stages?

Trophozoite – motile feeding stage    Cyst – dormant resistant stage

28.  What are the protozoan groups based on? List the protozoan pathogens associated with the Mastigophora group.

Locomotion and reproduction

-       Trypanosoma cruzi (Chagas), Leishmania, Giardia lamblia, and Trich Vaginalis

29.  List and describe the two groups of parasitic helminths.

Flatworms: flat, thin, segmentated body -tapeworms: long, ribbon like; flukes: flat, ovoid

Roundworms: round, elongate, cylindrical, unsegmented, spines, hooks -pinworms

30.  What is the difference between an enveloped and naked virus?

Enveloped has an envelope/covering around the capsid, naked do not

31.  List and describe the six stages of virus replication.

Adsorption: attachment to cell surface receptors

Penetration: fusion or endocytosis  release nucleic acid

Uncoating: release of the viral capsid and RNA into the cytoplasm

Duplication/Synthesis: takes control of cell  cell synthesizes the basic components of a new virus

Assembly: nucleocapsid and envelope are formed

Release: viruses bud off the membrane; virion is ready to infect other cells

32.  List examples of cytopathic effects caused by viruses.

Damage to host cells that alters their appearance

-       Cell lysis, alter DNA cancerous cells, change shape, fuse (RSV), damage

33.  What type of infections do prions cause? How are they spread? What is the name of the rapidly progressive neurodegenerative human prion disease?

Transmissible spongiform encephalopathies (TSEs)

-       spread by direct contact, contaminated foods  form hoes in nervous tissue

-       Creutzfeldt-Jakob disease

34.  Which microbes have the highest resistance to control?

Bacterial endospores

35.  What is the goal of sterilization?

Destroying endospores (kills all microbial life)

36.  Define microbiostatic and microbicide. Which microbicidal agent is considered a sterilizing agent?

Microbiostatic: process that temporarily prevent microbes from multiplytng

Microbicide: any chemical agent that kills pathogenic organisms

            -sporicide

37.   Define and give examples of sanitization, degermation, antisepsis, and disinfection.

Sanitization: any cleansing technique that mechanically removes microbes -dishwashing

Degermation: process to reduce the number of microbes on the human skin -surgical hand scrub

Antisepsis: process of using chemical agents on the skin to destroy or inhibit vegetative pathogens -antibacterial soap, preoperative iodine

Disinfection: any process to destroy vegetative pathogens, not endospores on inanimate objects -5% bleach, boiling water

38.  Define microbial death. List the factors that can affect an antimicrobial agent's mechanism of action.

Permanent loss of reproductive capability, even under optimum growth conditions

-       Number of microbes, nature of microbes in the population, temperature and pH of the environment, concentration of agent, mode of action of the agent, presences of solvents, organic matter, or inhibitors

39.  What are the four cellular targets that antimicrobial agents aim to destroy? Which antimicrobial agents are most effective for each cell target and why?

Cell wall (antibiotics, detergent, and alcohol), cell membrane (surfactants), cellular synthetic process of proteins and nucleic acids: DNA, RNA (antibiotics, chemicals, radiation), proteins structure and function (heat and chemicals)

40.  Is moist or dry heat more effective for microbial control? What is a common form of moist heat used in hospitals and medical offices to sterilize equipment?

Moist heat; autoclave

41.  What is desiccation and is it an effective method of sterilization?

Gradual removal of water from cells  metabolic inhibition; NO not effect method of microbial control, disinfection, or sterilization

42.  Differentiate ionizing and nonionizing radiation.

Ionizing: “cold”, deep penetrating, breaks DNA, gamma rays, xrays

Nonionizing: little penetrating, used to disinfect/sterilize air, water, and solid surfaces

43.  What is filtration? Give examples of substances that are best sterilized by filtration.

Mechanical removal of microbes by passing a gas or liquid through a filter

44.  Which heavy metals are used for antimicrobial control? What is silver sulfadiazine ointment commonly used for?

Silver and mercury; burn patients

45.  Differentiate narrow and broad-spectrum antimicrobial drugs and list the advantages and disadvantages of each.

Narrow: effective on a small range of microbes, target specific cell component

-       Advantages: cause less resistance of the bacteria

-       Disadvantages: causative organism must be identified

Broad: greatest range of activity, tart components common to most pathogens

-       Advantages: less need to identify the infecting agent before starting treatment

-       Disadvantages: increase rise to drug resistance

46.  What is the mechanism of action of beta-lactam antimicrobials? What are the most used beta-lactams?

Interfere with cell way synthesis; penicillins and cephalosporins

47.  Differentiate natural and semisynthetic penicillins and provide examples of each.

 Natural: do not penetrate the outer membrane and are less effective against G- bacteria; considered narrow spectrum (Pen G, Pen V)

Semisynthetic: cross the cell walls of G- bacteria and are broad spectrum (ampicillin, amoxicillin, carbenicillin)

48.  Carbapenems and monobactams are also beta-lactam drugs. List examples of each and state if they have broad or narrow spectrum coverage.

Carbapenems: broad (imipenem, meropenem)

Monobactams: narrow (aztreonam, only work on G-)

49.  Cephalosporins are a family of bacterial antibiotics structurally related to PCN and have a synthetically altered beta-lactam structure. What root names are associated with all generic cephalosporin medications? What type of bacteria are these medications most effective against and how has each successive generation of medication expanded its coverage?

-cef, ceph, or kef; G+; each group is more effective against G- than before

50.  List the antimicrobials discussed in class that disrupt cell membrane function.

Polymxins, daptomycins, amphotericin B, nystatin

51.  Which antimicrobials affect nucleic acid synthesis?

Fluoroquinolones, antiviral drugs that are analogs of pruines and pyrimidines

52.  How do fluroquinolones stop DNA replication and repair? What should you warn your patient about if you prescribe fluoroquinolone?

Bind and inhibit DNA gyrase and topoisomerases, stopping DNA replication and repair

-       Warnings of tendinosis and cardiac conduction issues

53.  Which ribosomal subunit do aminoglycosides target to disrupt protein synthesis? Are they broad or narrow spectrum? List the three aminoglycoside medications discussed in class. What other class of antibiotics target this ribosomal subunit?

30S: broad (Streptomycin, gentamicin, tobramycin); tetracyclines

54.  Which antimicrobials interfere with protein synthesis by targeting the 50s ribosomal unit? Which antimicrobials interfere with protein synthesis by targeting both the 30s and 50s ribosomal units?

-       Chloramphenicol, erythromycin, azithromycin, clarithromycin

-       Oxazolidinones

55.  Which medications have a mechanism of action that affects a microbe’s metabolic pathway?

Sulfamethoxazole, trimethoprim

56.  Define synergistic effect.

The effects of a combination of antibiotics are greater than the sum of the effects of the individual antibiotic

57.  What is the mechanism of action of antifungal medications?

Macrolide polyenes: nystatin, amphotericin B; crypto meningitis

Griseofulvin: treatment for ringworm and athletes foot

Synthetic azoles: ketoconazole, etc; vaginal suppositories; candidiasis, dermatophyte

Flucytosine: cutaneous mycoses

Echinocandins: damage cell wall of fungi w/o harming human cells; capsofungin, micafungin

58.  Create a table for antimalarial, antiprotozoal, and antihelminthic drugs.

Antimalarial: quinine, chloroquine, mefloquine, primaquine

Antiprotozoal: metronidazole

Anthelminthic: mebendazole, pyrantel, piperazine, ivermectin

59.   The goal of antiviral medications is to block a step in the completion of the virus cycle. List the modes of action of antiviral medications.

Blocking penetration of the virus not the host cell; blocking replication, transcription, or translation of viral genetic material; preventing the normal maturation of viral particles

60.  Which antiviral medications are also called anti-herpetics?

Acyclovir, valacyclovir, famiciclovir

61.  What is a superinfection?

An infection occurring during antibiotic therapy that is caused by an overgrowth of drug-resistant microorganisms

62.  What percentage of patients will experience a serious adverse reaction to antimicrobials? What is considered a major side effect?

5%; direct damage to tissue, allergic reactions, disruption in the balance of normal flora

63.  Define minimum inhibitory concentration.

Smallest concentration of drug that visibly inhibits growth

64.  Define therapeutic index. Is a high or low therapeutic index more desirable? Why?

Ratio of the dose of the drug that is toxic to humans as compared to its minimum effective dose; high, the lower it is the more toxic the drug

65.  Define normal flora, infection, pathogen, and disease. Define transient and resident microbes.

Normal flora: microbes that engage in mutual or commensal association w/ humans

Infection: condition in which pathogenic microbes penetrate host defenses, enter tissues, and multiply

Pathogen: infectious agent

Disease: infection that causes damage or disruption to tissues and organs

66.  Define microbial antagonism. What are endogenous and exogenous infections?

Microbial Antagonism: bacterial flora benefit host by preventing overgrowth of harmful microbes

Endogenous infection: occur when normal flora is introduced to a previously sterile site

Exogenous infection: caused by organisms not normally present in the body

67.  What is the largest and most accessible organ?

skin

68.  Which part of the body has the most diverse and unique flora, with more than 600 species?

Mouth

69.  Do human bites that break the skin typically require antibiotic coverage? Why?

Yes, increased risk of infection due to the high bacterial count

70.  How is the GI tract exposed to the environment? What type of bacteria does the intestinal environment favor? What is the name of the chemical that gives feces a characteristic odor?

Via oral cavity and anus; anaerobic bacteria; skatole

71.  List the three bacterial groups we discussed that are normal respiratory tract flora.

Streptococci, S. Aureus, Neisseria

72.  If a patient was being screened for MRSA, what is the most common location to swab for culture?

nose

73.  Changes in physiology influence the composition of the normal vaginal flora examples.

Estrogen, glycogen, pH

74.  List factors that can weaken host defenses and increase susceptibility to infection.

Old age, extreme youth, defects in immunity, surgery, organ transplants, organic disease, chemotherapy, physical and mental stress, other infections

75.  What are true and opportunistic pathogens?

True: capable of causing disease in a healthy person with normal immune defenses

Opportunistic: cause disease when the host’s defenses are compromised or when they grow in part of the body that is not natural to them

76.  Define virulence factor.

Any characteristic or structure of the microbe that contributes to the infection or disease

77.  What is the STORCH acronym?

Common infections of the fetus and neonate

S: syphilis, T: toxoplasmosis, O: other (Hep B, HIV, Chlamydia), R: rubella, C: cytomegalovirus, H: herpes simplex virus

78.  What is an infectious dose? Where does the initial response of host defenses come from?

Minimum number of microbes required for an infection to proceed; phagocytes

79.  How do pathogen exoenzymes affect the host? What can toxigenic pathogens produce?

Disrupt the structure of tissues; toxins

80.  Differentiate bacterial endotoxins and exotoxins. When are they secreted?

Endo: not secreted, released form cell after damage

Exo: secreted by a living bacterial cell into the infected issue, strong specificity

81.  List the targets of neurotoxins, enterotoxins, hemotoxins, and nephrotoxins.

Neuro: brain, entero: GI, hemo: blood, nephron: kidneys

82.  List and describe the 4 distinct stages of clinical infections.

Incubation: time from initial contact with the infectious agent to the appearance of first symptoms; agent is multiplying but no symptoms present

Prodromal: vague feelings of discomfort; nonspecific complaints

Invasion: multiplies at high levels, become well-establish, specific signs and symptoms

Convalescent: person begins to respond to the infection, symptoms decline

83.   Define local, systemic, focal, mixed, and primary-secondary infections and give examples of each.

Local: confined to a specific site (boils, warts, fungal skin infections)

Systemic: spreads to several sites and tissue fluids like the bloodstream (measles, typhoid, syphilis, rubella, chickenpox, histoplasmosis, cryptococcosis)

Focal: local spreads to systemic (TB, streptococcal pharyngitis)

Mixed: several microbes grow simultaneously at the same site (human bits, dental carries, gas gangrene, wound infections)

Primary-secondary: an initial infection is complicated by a second one in the same or different location and caused by a different microbe

84.  Differentiate asymptomatic and latent infections.

Asymptomatic: host doesn’t show any signs of disease despite being infected

Latent: periodically becomes active and produce recurrent disease

85.  Who is a living reservoir carrier?

Humans, animals, soil, water, plants

86.  Differentiate incubation, convalescent, and chronic carriers?

Incubation: spread the infectious agent during the incubation period

Convalescent: recuperating w/o symptoms, but still shed viable microbes

Chronic: shelters the infectious agent for a long period after recovery

87.   What is a vector? Give examples of biological and mechanical vectors.

Live animal (non-human) that transmits an infectious agent from one host to another

-       Biological: mosquitos, fleas

-       Mechanical: houseflies, cockroaches

88.  What is a zoonotic disease?

Disease indigenous to animals but spreads to humans

89.  What is the difference between a communicable and non-communicable disease? What is a nosocomial infection?

Communicable: infection can spread from one host to another; contagious

Non-communicable: does not transfer from one person to another

Nosocomial: acquired or developed during a hospital stay

90.  Describe the patterns of infectious disease occurrence. Include endemic, sporadic, epidemic, and pandemic

Endemic: relatively steady frequency over long period of time in a particular area

Sporadic: occasional cases are reported at irregular intervals

Epidemic: prevalence of a disease is increasing beyond expected

Pandemic: epidemic across continents