Chapter 15 Reading Worksheet Name:__________________________

How Microorganisms Enter A Host

1. Define portal of entry:- The avenue by which a pathogen gains access to the body

2. List three common portals of entry:1) Mucus membranes2) Skin3) Direct deposition

3. Describe what is meant by “the parenteral route” and give 5 examples of how microorganisms might enter via this route:

- A portal of entry for pathogens by deposition directly into tissues beneath the skin and mucus membranes

- A break in the skin- Animal bite- Needle-stick- Incision

4. a. Define and distinguish between ID50 and LD50:- ID50: The number of microorganisms required to produce a demonstrable

infection in 50% of the test host population- LD50: The lethal dose for 50% of the inoculated hosts within a given period

b. Given the following ID50 values for anthrax, indicate through which portal of entry it is easiest to get anthrax:__1__Cutateous: 50 endospores__2__Inhaltion: 20,000 endospores__3__Ingestion: 1,000,000 endospores____All are equal

c. Based on the following ID50 values, which organism is most virulent, assuming they enter through the proper portal of entry:

__2__Cryptosporidium 50 cells__3__E.coli O157:H7 1000 cells__1__Shigella spp. 10 cells__4__Vibria cholerae 108 cells

What do each of the microorganisms in this question have in common?

d. Generally, the more virulent a microorganism, the ___smaller___ (smaller/larger) the ID50.

5. a. How do microorganisms adhere to the host’s tissues? __adherence__ b. Adherence molecules on microorganisms are called ___adhesins or ligands____.

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c. Complementary molecules on host to which microorganisms adhere are called __receptors__

d. Adhesins (ligands) are generally found ___on surface___ (on surface/inside) of microorganisms.

e. Name several bacterial structures on which adhesions may be located: __glycocalyx, pili, fimbriae, flagella__f. How does Streptococcus mutans adhere to teeth?

- Glycocalyxg. How does Actinomyces adhere to S. mutans?

- Fimbriaeh. What clinical problem do S. mutans and Actinomyces cause in humans?

- They make up dental plaque and contribute to dental caries (tooth decay)

6. a. Define biofilm:- Microbial community that usually forms as a slimy layer on a surface

b. List several examples of circumstances where biofilms play an important role?- Dental plaque on teeth, algae on walls of swimming pools, scum that

accumulates on shower doors

7. For each microorganism listed, indicate the mechanism it uses to adhere to the host:

a. Enteropathogenic strains of E. coli:- Adhesions on fimbriae that adhere only to specific kinds of cells in

certain regions of the small intestineb. Treponema pallidum:

- Causative agent of syphilis – uses its tapered end as a hook to attach to host cells

c. Neisseria gonorrhoeae:- Causative agent of gonorrhea – fimbriae containing adhesins which

permit attachment to cells with appropriate receptors in the genitourinary tract, eyes, and pharynx

How Bacterial Pathogens Penetrate Host Defenses:

8. Describe the role that capsules play in bacterial virulence:- Resists the host’s defenses by impairing phagocytosis

9. List 4 different pathogenic bacteria (genus/species names) that produce capsules:1) Streptococcus pneumoniae 2) Klebsiella pneumoniae 3) Haemophilus influenzae4) Bacillus anthracis

10. Does the presence of a capsule automatically enable a microorganism to cause disease? - NO

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11. How does M-protein (a cell wall component of Group A streptococci) contribute to its virulence? (2 ways)

1) Heat-resistant2) Acid-resistant

12. How do the waxes in Mycobacterial cell walls contribute to their virulence?- Increases virulence by resisting digestion by phagocytes – bacteria can even

multiply inside phagocytes

13. Briefly describe the activity of each of these bacterial enzymes and name an organism that produces each:

a. Coagulase:- Bacterial enzyme that coagulates/clots the fibrinogen in blood- Staphylococcus

b. Kinases (fibrinolysin/streptokinase):- Bacterial enzyme that breaks down fibrin digests clots formed by the

body to isolate an infection - Streptococcus pyogenes

How can streptokinase be used to benefit a patient?- Digesting blood clots in coronary arteries- Treating deep vain thrombosis - Dissolving clots in IV catheters

c. Hyaluronidase:- Enzyme secreted by certain bacteria that hydrolyzes hyaluronic acid and

helps spread microorganisms from their initial site of infection - Streptococci

d. Collagenase:- Enzyme that hydrolyzes collagen – facilitating spread of gas gangrene - Clostridium

e. IgA protease:- Enzymes that destroy antibodies that defend against adherence of

pathogens to mucosal surfaces- N. gonorrhoeae, N. meningitidis

14. How does antigenic variation affect an organism’s virulence?- Alteration of surface antigens – by the time body mounts an immune response

against pathogen, pathogen has already altered its antigens and is unaffected by the antibodies

- Some microbes can activate alternative genes resulting in antigenic changes

What are 2 examples of common microbes that make use of antigenic variation to evade host defenses:

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1) Influenzavirus (causative agent of the flu)2) Neisseria gonorrhoeae (causative agent of gonorrhea)

15. What is an invasin?- Surface protein produced by Salmonella typhimurium and Escherichia coli that

rearranges nearby actin filaments in the cytoskeleton of a host cell

How Bacterial Pathogens Damage Host Cells16. Define siderophore:

- Bacterial iron-binding proteins

17. Define toxin:- Poisonous substance produced by a microorganism

18. Define toxigenicity:- Capacity of a microorganism to produce a toxin

19. Define toxemia:- Presence of toxins in the blood

20. Define exotoxin and list several characteristics of exotoxins:- Protein toxin released from living, mostly gram-positive bacterial cells- Produced inside some bacteria as part of their growth and metabolism and are

secreted by bacterium into surrounding medium or released following lysis - Characteristics

- Proteins- Many are enxymes that catalyze only certain biochemical reactions

- Even small amounts harmful because they can act over and over again- Produced inside bacterial cell- Secreted into external environment- Most (NOT ALL) associated with gram positives

21. Define toxoid:- Exotoxin inactivated by heat, formaldehyde, iodine, other chemicals that can

no longer cause disease but can still stimulate body to produce antitoxins

22. Define antitoxin:- Specific antibody produced by the body in response to a bacterial exotoxin or

its toxoid

23. List several examples of membrane-disrupting toxins and name the microorganism that produces each:

- Leukocidins: substances produced by some bacteria that can destroy neutrophils and macrophages – kill phagocytic leukocytes – act by forming protein channels

- Staphylococci and Streptococci - Hemolysins: destroy erythrocytes (RBC), also by forming protein channels

- Staphylococci and Streptococci

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- Streptolysins: hemolysins produced by streptococci

24. Define superantigen and give two examples:- Antigen that activates many different T cells elicits large immune response

due to release of cytokines from host cells1) Staph. aureus 2) Strep. pyogenes

25. Define genotoxins- Damage DNA – causes mutations, disrupts cell division, may lead to cancer- Made by some gram-negative bacteria

26. Briefly describe the activity of each of the following exotoxins: (Table 15.2)a. Diphtheria toxin:

- Cytotoxin inhibits protein synthesis, especially in nerve, heart, and kidney cells

b. Erythrogenic toxin:- Causes massive red blood cell destruction

c. Botulinum toxin:- Neurotoxin prevents transmission of nerve impulses; flaccid paralysis

results

d. Tetanus toxin:- Neurotoxin blocks nerve impulses to muscle relaxation pathway; results

in uncontrollable muscle contractions

e. Vibrio enterotoxin:- Enterotoxin causes secretion of large amounts of fluids and electrolytes

that result in diarrhea

f. Staphylococcal enterotoxin:- Enterotoxin causes secretion of fluids and electrolytes that results in

diarrhea

g. Staphylococcal exfoliative toxin (exfoliatin):- Exotoxin causes skin layers to separate and slough off

h. Staphylococcal TSST1- Toxin causes secretion of fluids and electrolytes from capillaries that

decreases blood volume and lowers blood pressure

27. Define endotoxin:- Part of outer portion of cell wall (lipid A) of most gram-negative bacteria –

released on destruction of the cell

28. Describe the physiological effects of endotoxin on humans:

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- Chills, fever, weakness, generalized aches, in some cases – shock and even death, can induce miscarriage

29. What part of the bacterial cell (be very specific) is endotoxin derived from?- Lipid portion of lipopolysaccharides – lipid A

30. Which of the following groups of bacteria make endotoxin?

Gram positives?- NO

Gram negatives?- YES

31. Describe the stepwise process through which endotoxins induce a fever response:

1) Macrophage ingests a gram-negative bacterium2) Bacterium is degraded in a vacuole, releaseing endotoxins that induce

macrophage to produce cytokines, interleukin-1, and tumor necrosis factor alpha 3) Cytokines are released into the bloodstream by macrophages, through which

they travel to the hypothalamus (temperature control center of brain)4) Cytokines induce the hypothalamus to produce prostaglandins – reset body’s

“thermostat” to a higher temperature producing fever

32. Define septic shock:- Sudden drop in blood pressure induced by bacterial toxins

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BE SURE TO READ THROUGH AND STUDY TABLE 15.3.

Pathogenic Effects of Viruses:Long 2016

33. Define cytopathic effects (CPE):- Visible effect on a host cell, caused by a virus, that may result in host cell

damage or death

34. List at least 5 examples of viral CPE:1) Macromolecular synthesis within host cell stops – some viruses (herpes

simplex virus) irreversibly stop mitosis2) Host cell lysosomes are made to release their enzymes, resulting in

destruction of intracellular contents and host cell death3) Inclusion bodies, granules or viral particles, are found in the cytoplasm or

nucleus of some infected cells – important in helping identify the causative agent of infection

4) Syncytium: multinucleated giant cell resulting from certain viral infections 5) Changes in host cell’s functions with no visible changes in the infected cells6) Induction of antigenic changes on the surface of the infected cells – elicit a

host antibody response against infected cell, thus target cell for destruction by host’s immune system

7) Chromosomal changes in the host cell8) Transformation of host cells by viruses capable of causing cancer – results in

an abnormal, spindle-shaped cell that does not recognize contact inhibition cells don’t stop growing when they come in close contact with other cells – results in unregulated cell growth

9) Some virus-infected host cells produce substances called alpha and beta interferons

35. List several virulence factors of fungi.- Trichothecenes: fungal toxins that inhibit protein synthesis in eukaryotic cells

- Ingestion causes headaches, chills, severe nausea, vomiting, visual disturbances

- Candida albicans and Trichophyton secrete proteases – enzymes may modify host cell membranes to allow attachment of the fungi

- Cryptococcus neoformans produces capsule that helps resist phagocytosis - Claviceps purpurea: produces ergot toxin that causes ergotism

- Cause hallucinations, constriction of capillaries, cause gangrene of limbs by preventing proper blood circulation in body

- Aflatoxin: carcinogenic toxin produced by growth of mold Aspergillus flavus- Mycotoxins: produced by some mushrooms – phalloidin, affects plasma

membrane function, and amanitin, affects RNA synthesis

36. List several virulence factors of protozoa.- Plasmodium (causative agent of malaria) invades host cells and reproduces

within them – causing their rupture - Toxoplasma attaches to macrophages and gains entry by phagocytosis –

prevents normal acidification and digestion, can grow in phagocytic vacuole - Giardia intestinalis (causative agent of giardiasis) attaches to host cells by a

sucking disc and digests the cells and tissue fluids

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- Some can evade host defenses and cause disease for very long periods of time: Giardia and Trypanosoma use antigenic variation to stay one step ahead of host’s immune system

37. Define Portal of Exit:- Route by which a pathogen leaves the body – secretions, excretions,

discharges, or tissue that has been shed- In general, relate to infected part of body – microbes tend to use same portal

for entry and exit- Let pathogens spread through population by moving from one susceptible host

to another

Fig. 15.9 provides an excellent review of the chapter.

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