Deck 15: Microbial Mechanisms of Pathogenicity

Question 1

All of the following contribute to a pathogen's invasiveness EXCEPT

A)toxins.
B)capsules.
C)cell wall components.
D)hyaluronidase.
E)coagulases.

Answer 1

A

Question 2

All of the following are examples of entry via the parenteral route EXCEPT

A)injection.
B)bite.
C)surgery.
D)hair follicle.
E)skin cut.

Answer 2

D

Question 3

All of the following are used by bacteria to attach to host cells EXCEPT

A)M protein.
B)ligands.
C)fimbriae.
D)capsules.
E)A-B toxins.

Answer 3

E

Question 4

Siderophores are bacterial proteins that compete with the host's

A)antibodies.
B)red blood cells.
C)iron-transport proteins.
D)white blood cells.
E)receptors.

Question 5

Which of the following statements is FALSE?

A)Leukocidins destroy neutrophils.
B)Hemolysins lyse red blood cells.
C)Hyaluronidase breaks down substances between cells.
D)Kinase destroys fibrin clots.
E)Coagulase destroys blood clots.

Question 6

Which of the following statements about exotoxins is generally FALSE?

A)They are more potent than endotoxins.
B)They are composed of proteins.
C)They are resistant to heat.
D)They have specific methods of action.
E)They are produced by gram-positive bacteria.

Question 7

The ability of some microbes,such as Trypanosoma or Giardia to alter their surface molecules and evade destruction by the host's antibodies is called

A)antigenic variation.
B)lysogenic conversion.
C)virulence.
D)cytopathic effect.
E)cytocidal effect.

Question 8

All of the following organisms produce exotoxins EXCEPT

A)Salmonella typhi.
B)Clostridium botulinum.
C)Corynebacterium diphtheriae.
D)Clostridium tetani.
E)Staphylococcus aureus.

Question 9

The most frequently used portal of entry for pathogens is the

A)mucous membranes of the respiratory tract.
B)mucous membranes of the gastrointestinal tract.
C)skin.
D)parenteral route.
E)All of these portals are used equally.

Question 10

The fimbriae of Neisseria gonorrhea and enteropathogenic E.coli are examples of

A)adhesins.
B)ligands.
C)receptors.
D)adhesins and ligands.
E)adhesins,ligands,and receptors.

Question 11

All of the following are methods of avoiding host antibodies EXCEPT

A)antigenic changes.
B)IgA proteases.
C)invasins.
D)membrane-disrupting toxins.
E)inducing endocytosis.

Question 12

Endotoxins are

A)associated with gram-positive bacteria.
B)molecules that bind nerve cells.
C)part of the gram-negative cell wall.
D)excreted from the cell.
E)A-B toxins.

Question 13

Which disease-associated fungi or fungal characteristics are mismatched?

A)ergot - sclerotia
B)trichothecenes - inhibit protein synthesis
C)Cryptococcus neoformans - capsules
D)Claviceps purpura - aflatoxin
E)Amantia - neurotoxin

Question 14

Botulism is caused by ingestion of a proteinaceous exotoxin;therefore,it can easily be prevented by

A)boiling food prior to consumption.
B)administering antibiotics to patients.
C)not eating canned food.
D)preventing fecal contamination of food.
E)filtering food.

Question 15

Most pathogens that gain access through the skin

A)can penetrate intact skin.
B)just infect the skin itself.
C)enter through hair follicles and sweat ducts.
D)must adhere first while their invasive factors allow them to penetrate.
E)must be injected.

Question 16

Which of the following is NOT a membrane-disrupting toxin?

A)A-B toxin
B)hemolysin
C)leukocidin
D)streptolysin O
E)streptolysin S

Question 17

Superantigens produce intense immune responses by stimulating lymphocytes to produce

A)endotoxins.
B)exotoxins.
C)cytokines.
D)leukocidins.
E)interferons.

Question 18

The ID₅₀ is

A)a measure of pathogenicity.
B)the dose that will cause an infection in 50 percent of the test population.
C)the dose that will kill some of the test population.
D)the dose that will cause an infection in some of the test population.
E)the dose that will kill 50 percent of the test population.

Question 19

Cytopathic effects are changes in host cells due to

A)viral infections.
B)protozoan infections.
C)fungal infections.
D)bacterial infections.
E)helminthic infections.

Question 20

Which of the following cytopathic effects is cytocidal?

A)inclusion bodies
B)giant cells
C)antigenic changes
D)transformation
E)release of enzymes from lysosomes

Question 21

Antibiotics can lead to septic shock if used to treat

A)viral infections.
B)gram-negative bacterial infections.
C)gram-positive bacterial infections.
D)protozoan infections.
E)helminth infestations.

Question 22

Endotoxins in sterile injectable drugs could cause

A)infection.
B)septic shock symptoms.
C)giant cell formation.
D)nerve damage.
E)no damage,because they are sterile.

Question 23

Cholera toxin polypeptide A binds to surface gangliosides on target cells.If the gangliosides were removed,

A)polypeptide A would bind to target cells.
B)polypeptide A would enter the cells.
C)polypeptide B would not be able to enter the cells.
D)Vibrio would not produce cholera toxin.
E)Vibrio would bind to target cells.

Question 24

Gram-negative septic shock results from the following events.What is the second step?

A)Body temperature is reset in the hypothalamus.
B)Fever occurs.
C)IL-1 is released.
D)LPS is released from gram-negative bacteria.
E)Phagocytes ingest gram-negative bacteria.

Question 25

Symptoms of intense inflammation and shock occur in some gram-positive bacterial infections due to

A)A-B toxins.
B)lipid A.
C)membrane-disrupting toxins.
D)superantigens.
E)erythrogenic toxin.

Question 26

All of the following bacteria release endotoxin EXCEPT

A)Clostridium botulinum.
B)Salmonella Typhi.
C)Neisseria meningitidis.
D)Proteus vulgaris.
E)Haemophilus influenzae.

Question 27

Table 15.1
Table 15.1 shows the ID₅₀ for Staphylococcus aureus in wounds with and without the administration of ampicillin before surgery.Based on the data,the administration of ampicillin before surgery

A)decreases the risk of staphylococcal infection.
B)increases the risk of staphylococcal infection.
C)has no effect on risk of infection.
D)replaces tetracycline.
E)The answer cannot be determined based on the information provided.

Question 28

Injectable drugs are tested for endotoxins by

A)the Limulus amoebocyte lysate test.
B)counting the viable bacteria.
C)filtering out the cells.
D)looking for turbidity.
E)culturing bacteria.

Question 29

Bacteria such as E.coli and Salmonella produce invasins that bind host cells,thus causing the cells to

A)release TNF.
B)produce iron-binding proteins.
C)engulf the bacteria.
D)destroy the bacteria.
E)release cytokines.

Question 30

Which of the following is an example of direct damage due to bacterial infection?

A)the uncontrolled muscle contractions in Clostridium tetani infection
B)the invasion and lysis of intestinal cells by E.coli
C)the hemolysis of red blood cells in a staphylococcal infection
D)the fever,nausea,and low blood pressure in a Salmonella infection
E)the excessive secretion of fluids in a Vibrio cholera infection

Question 31

Twenty-five people developed symptoms of nausea,vomiting,and diarrhea three to six hours after attending a church picnic where they ate a ham and green bean casserole with cream sauce.The most likely cause of this case of food intoxication is

A)botulinum toxin.
B)aflatoxin.
C)staphylococcal enterotoxin.
D)erythrogenic toxin.
E)cholera toxin.

Question 32

Polio is transmitted by ingestion of water contaminated with feces containing polio virus.What portal of entry does polio virus use?

A)skin only
B)parenteral only
C)mucous membranes only
D)skin and parenteral
E)skin,parenteral,and mucous membranes

Question 33

Which of the following statements about M protein is FALSE?

A)It is found on Streptococcus pyogenes.
B)It is found on fimbriae.
C)It is heat- and acid-resistant.
D)It is readily digested by phagocytes.
E)It is a protein.

Question 34

Which of the following statements about staphylococcal enterotoxin is FALSE?

A)It causes vomiting.
B)It causes diarrhea.
C)It is an exotoxin.
D)It is produced by Staphylococcus aureus growing in the host's intestines.
E)It is a superantigen.

Question 35

Which of the following contributes to the virulence of a pathogen?

A)numbers of microorganisms that gain access to a host
B)evasion of host defenses
C)toxin production
D)numbers of microorganisms that gain access to a host and evasion of host defenses
E)numbers of microorganisms that gain access to a host,evasion of host defenses,and toxin production

Question 36

Lysogenic bacteriophages contribute to bacterial virulence because bacteriophages

A)give new gene sequences to the host bacteria.
B)produce toxins.
C)carry plasmids.
D)kill the bacteria,causing release of endotoxins.
E)kill human cells.

Question 37

Table 15.2

Which organism in Table 15.2 most easily causes an infection?

A)E)coli O157:H7
B)Legionella pneumophila
C)Shigella
D)Treponema pallidum
E)The answer cannot be determined based on the information provided.

Question 38

Symptoms of protozoan and helminthic diseases are due to

A)tissue damage due to growth of the parasite on the tissues.
B)waste products excreted by the parasite.
C)products released from damaged tissues.
D)tissue damage due to growth of the parasite on the tissues and waste products excreted by the parasite.
E)tissue damage due to growth of the parasite on the tissues,waste products excreted by the parasite,and products released from damaged tissues.

Question 39

Which of the following is NOT a cytopathic effect of viruses?

A)cell death
B)host cells fusing to form multinucleated syncytia
C)inclusion bodies forming in the cytoplasm or nucleus
D)increased cell growth
E)toxin production

Question 40

Which of the following mechanisms is used by gram-negative bacteria to cross the blood-brain barrier?

A)producing fimbriae
B)inducing endocytosis
C)producing toxins
D)inducing TNF
E)antigenic variation

Question 41

In A-B exotoxins,the A component binds to the host cell receptor so that the B component can enter the cell.

Question 42

Many pathogens use the same portal for entry and exit from the body.

Question 43

The Limulus amoebocyte assay is used to detect minute amounts of endotoxin in drugs and medical devices.

Question 44

Most symptoms of endotoxins can be treated with administration of anti-endotoxin antibodies.

Question 45

In response to the presence of endotoxin,phagocytes secrete tumor necrosis factor.This causes

A)the disease to subside.
B)a decrease in blood pressure.
C)a fever.
D)a gram-negative infection.
E)an increase in red blood cells.

Question 46

Nonpathogenic Vibrio cholerae can acquire the cholera toxin gene by

A)phagocytosis.
B)lysogenic conversion.
C)conjugation.
D)transformation.
E)infecting a pathogenic Vibrio cholerae.

Question 47

Which is NOT specifically employed by pathogens to avoid destruction by phagocytosis?

A)producing a capsule
B)possessing ability to replicate within a phagolysosome
C)producing superantigens
D)possessing ability to remain dormant within a phagocyte
E)forming biofilms

Question 48

The M protein enhances the virulence of Streptococcus by preventing phagocytosis.

Question 49

For what reason might the ID50 for Salmonella Typhi decrease when a rat simultaneously ingests sulfa drugs with the pathogen?

A)It would not;the ID50 goes up.
B)The antimicrobial interferes with the microbiome enabling the pathogen to more easily establish infection.
C)There would not be an effect on the ID50.
D)The antimicrobial inactivates stomach acid and allows the pathogen to more readily pass to the intestine.
E)Salmonella Typhi becomes stronger in the presence of sulfa drugs.

Question 50

Cytopathic effects,such as inclusion bodies and syncytium formation,are the visible signs of viral infections.

Question 51

Bacteria that cause periodontal disease have adhesins for receptors on streptococci that colonize on teeth.This indicates that

A)streptococci get bacterial infections.
B)streptococcal colonization is necessary for periodontal disease.
C)bacteria that cause periodontal disease adhere to gums and teeth.
D)bacteria that cause periodontal disease adhere to teeth.
E)streptococci cause periodontal disease.

Question 52

Ergot and aflatoxin are toxins sometimes found in grains contaminated with fungi.

Question 53

Table 15.2

Which organism in Table 15.2 causes the most severe disease?

A)E)coli O157:H7
B)Legionella pneumophila
C)Shigella
D)Treponema pallidum
E)It cannot be determined from the information provided.

Question 54

Patients developed inflammation a few hours following eye surgery.Instruments and solutions were sterile,and the Limulus assay was positive.The patients' inflammation was due to

A)bacterial infection.
B)viral infection.
C)endotoxin.
D)exotoxin.
E)The answer cannot be determined based on the information provided.

Question 55

Biofilms provide pathogens with an adhesion mechanism and aid in resistance to antimicrobial agents.

Question 56

A retired contract administrator who enjoyed gardening sought medical attention for what appeared to be a sinus infection.He received antimicrobials but the conditioned worsened and he was experiencing severe painful spasms in his jaw.He admitted to injuring himself with a gardening tool while wearing sandals in the yard but did not seek medical attention for the wound.The man is likely experiencing

A)septic shock.
B)LPS-mediated inflammatory response.
C)intoxication caused by a focal C.tetani infection.
D)allergic rhinitis.
E)meningitis.

Question 57

Infections with some viruses may induce chromosomal changes that alter the growth properties of host cells.

Question 58

The best description of direct damage by a pathogen is

A)host cells destroyed when pathogens metabolize and multiply.
B)capsule components of pathogens kill cells.
C)poisonous substances secreted by viruses kill cells.
D)superantigens cause cytokine release which then cause symptoms of disease.
E)protein synthesis is interrupted by toxins.

Question 59

In general,the LD₅₀ for exotoxins is much greater than the LD₅₀ for endotoxins.

Question 60

Which pathogen and virulence factor are mismatched?

A)Streptococcus pneumoniae - capsule
B)Streptococcus pyogenes - M protein
C)Clostridium - hyaluronidase
D)Shigella sonnei - coagulase
E)Neisseria gonorrhoeae - IgA protease

Question 61

Some pathogens evade phagocytosis,while other pathogens evade host defenses by entering host cells.Discuss the advantages and disadvantages of both of these evasion strategies.

Question 62

Compare and contrast endotoxins and exotoxins.Why are exotoxins more potent than endotoxins?

Question 63

Antibiotics can kill gram-negative bacteria,but symptoms of fever and low blood pressure can persist.Why?