MIP 300 Exam 2

Describe at least 3 factors that help determine whether a microbe will cause a disease in a particular host.

the number of organisms inoculated, virulence of the organism, and the hosts degree of resistance all help determine if a microbe will cause disease

What is the difference between pathogenicity and virulence?

Pathogenicity is the organisms fundamental ability to cause disease. Virulence is the intensity of pathogenicity, measured by mortality

Define “signs” and “symptoms.”

Symptoms are subjective feelings like nausea while signs are objective observable indications of disease

Explain the iceberg theory of infection.

Suggests that the majority of infections are asymptomatic

List 3 factors that can affect virulence.

infectivity, invasiveness, and pathogenic potential which is the ability to cause signs and symptoms

List 4 factors that affect infectivity.

The ability to be transferred to a host, adhere and colonize in the host, then grow while avoiding the hosts immune system influence infectivity

What is direct transmission and what are the examples we discussed in class?

Direct transmission involves immediate contact such as horizontal contact (kissing), vertical contact (mother to baby), airborne droplets, or vectors/insects

What is indirect transmission and what are the examples we discussed in class?

Indirect transmission of disease is through things like contaminated food, water or inanimate objects like doorhandles

Define “fomites” and describe how they contribute to the transmission of disease.

Fomites are inanimate objects that can become contaminated with pathogens that can be transmitted

What is the function of adhesins and recognize why they are important to virulence?

Adhesins are microbial molecules that allow microbes to stick to specific receptors on host cells. They are important to virulence as they counteract the bodies defenses attempting to wash cells away

Give examples of ways microbes can evade the host immune system, at least initially.

Initially microbes can secrete enzymes to destroy the immune cells, use physical barriers like capsules, or can survive inside macrophages

Define microbial invasiveness, and give examples of microbial products that are used for invasion by microbes.

the ability of a microbe to spread within host tissues using products to break down cellular connections. some of these produces can break down membranes, degrade connective tissue, and prevent cells from adhering to each other

Define and describe pathogenic potential.

Pathogenic potential is the microbe's mechanical or chemical ability to cause host damage

Differentiate between an infection and an intoxication.

An infection occurs when a pathogen enters the host, multiplies, and produces virulence factors within the body. Intoxication occurs when a microbe produces toxins outside of the hosts which are then are toxic when ingested

Please describe one neurotoxin. Name an organism that releases each of these toxins.

Botulinum toxin released by C. botulinum affects the nervous system

Please describe one enterotoxin. Name an organism that releases this toxin

Cholera toxin released by V. cholerae stops water uptake in the intestines causing diarrhea

Please describe one cytotoxin. Name an organism that releases this toxin

Diphtheria toxin released by C. diphtheriae inhibits protein synthesis leading to cell death

Describe the difference between how botulism and tetanus toxins work. How does this explain the symptoms each type causes?

Botulism toxin inhibits stimulatory neurotransmitters resulting in flaccid paralysis. Tetanus toxin inhibits inhibitory neurotransmitters leading to spastic paralysis

Discuss how superantigens affect the body and give an example of one microbe that produces a superantigen as its exotoxin.

Superantigens are exotoxins that overstimulate the immune system by artificially binding T-cell receptors to immune cells, leading to a massive release of cytokines that can cause low blood pressure. Staph is a superantigen producer

Compare and contrast endotoxins and exotoxins, and discuss which types of bacteria can make these.

Exotoxins are proteins secreted by G± bacteria that are highly toxic and specific while endotoxins are the lipid a component on g- bacteria that elicit a more general immune response

Explain how both exotoxins and endotoxins can lead to shock, but by different pathways.

Exotoxins lead to shock by the massive artificial activation of T cells while endotoxins activate blood clotting factors which leads to unregulated clotting in capillaries and organ failure

Compare and contrast toxoids and antitoxins.

Toxoids are toxins inactivated by heat or chemicals used in vaccines while antitoxins are premade antibodies that neutralize toxins already circulating

Discuss how an immune response to a pathogen can cause damage.

An immune response can cause immune cells to release toxic molecules intended for the microbe that damage healthy tissue or antigen antibody complexes can settle in the body and cause localized tissue destruction through the complement cascade

Please describe a symbiotic relationship that is commensal in nature

One organism benefits while the other is neither helped nor harmed

Please describe a symbiotic relationship that is parasitic

the parasite benefits at the expense of the host, often causing disease

Please describe a symbiotic relationship that is mutualistic.

Both parties benefit from the interaction. Deep sea tube worms that provide protection to bacteria which then provide them with organic matter

Describe where in the body you can find normal flora. What type of symbiotic relationship do you think the organisms you described are having with the host (parasitic, mutualistic, commensal)?

Normal flora resides on the bodys surface. Modern research suggest normal flora is mutalistic

Compare and contrast colonization and infection.

Colonization is the routine residence of microbes on host surfaces and is typically mutualistic. An infection occurs when microbes cause disease, becoming parasitic

Which locations/organs should be sterile?

Areas of the body that have no contact with the external environment should be sterile

Discuss the role of the mucociliary escalator.

Consists of ciliated columnar cells and a mucus layer that traps inhaled microbes and allows them to be expelled

Describe the three ways normal flora can be protective.

They compete with pathogenic bacteria for space, they produce substances that can kill competing pathogens, they produce beneficial chemicals that can help train the immune system

Which parts of the respiratory tract should be sterile? explain why

The lower respiratory tract has the lowest amount of microbes but none of the respiratory tract is completely sterile

Discuss when normal flora can be harmful.

Normal flora can become opportunistic and cause harm when they overgrow. This occurs most commonly during surgery, injury, or immunosuppression

Explain the purpose of a fecal transplant, and discuss who is most likely to be the donor and why.

The purpose of a fecal transplant is to repopulate a patients gut with healthy normal flora to outcompete a persistent pathogen. The most likely donor is a housemate because their gut flora naturally resembles the patient

When is a Clostridium difficile infection is likely to occur?

C. diff most likely occurs following a course of antibiotics because antibiotics kill normal flora leaving space for c. diff to grow

Explain what an antigen is.

A self or nonself substance that the body recognizes as foreign, eliciting an immune response

List the 6 ways the innate immune response protects you against infection, and explain what it means when we say it is “nonspecific” or “innate.”

Innate responses are nonspecific and provide general protection against many substances. These defenses include physical and chemical barriers, molecular and cellular defenses, inflammation, and fever

Describe how skin is an innate physical barrier and discuss the microbe’s response to get past the skin barrier.

The epidermis consists of tightly packed keratinocytes that constantly shed and make it difficult for microbes to invade. Some pathogens produce enzymes that physically invade the skin

Discuss the ways in which mucous membranes in the respiratory, GI and genitourinary tracts form a protective barrier that inhibits the penetration of microbes.

The respiratory tract uses the mucociliary escalator to trap microbes and propel them out. The genitourinary tract uses urinary flushing, cervical mucus, and prostatic fluid containing antimicrobial enzymes. The GI tract uses peristalsis, saliva, and stomach acid to prevent pathogenesis

Describe the microbe’s response to mucous membranes. What can weaken these mucosal defenses?

Pathogens may have strong adhesins or capsules to resist being washed away by saliva. Some, like Vibrio cholerae, have flagella to swim through mucus, while others like Helicobacter pylori can neutralize stomach acid. Mucosal defenses can be weakened by smoking, asthma, cystic fibrosis

Identify at least one innate physical, chemical, molecular and cellular defense/barrier.

A physical barrier is the skin, chemical is lysozyme, molecular is complement proteins, cellular is macrophages

Explain what complement is and identify its main functions

Complement is a system of 20 different proteins produced by the liver that circulate in the plasma and activate in a cascade upon encountering a pathogen. Its main functions are opsonization/enhancing phagocytosis, direct lysis, and inducing inflammation

Describe the membrane attack complex (MAC)

The MAC is formed when complement proteins polymerize and insert themselves into the membrane of a bacterium creating a hole in the microbe

Explain the function of cytokines in the immune response. Specifically describe the function of Type I Interferons (IFN).

Cytokines are proteins that are responsible for intracellular signaling. Type 1 IFN binds neighboring uninfected cells and signals them to produce antiviral proteins that degrade viruses

Describe the difference between granulocytes and agranulocytes and give examples of each.

Granulocytes contain granules filled with toxic molecules to break down invaders (Neutrophils). Agranulocytes lack toxic granules, for example macrophages and dendritic cells

Explain what phagocytosis is, and identify the immune cells that are capable of phagocytosis.

Phagocytosis is the process by which immune cells engulf foreign material so they can degrade it

List the four major benefits of fever against bacteria and explain why each is beneficial to the host.

Fevers slow microbe growth rates, inactivate heat sensitive toxins, increase immune activity, and make the host feel bad to increase the likelihood of rest