Deck 10: Pathogenic Mechanisms and Evasion Strategies of Microorganisms

Question 1

Which of the following enzymes produced by some bacteria is used therapeutically to dissolve fibrin clots?

A)Coagulase.
B)Streptokinase.
C)Hyaluronidase.
D)Collagenase.
E)Keratinase.

Answer 1

B

Question 2

Streptokinase

A)is an enzyme that breaks down fibrin.
B)is an endotoxin of Streptococcus.
C)coagulates fibrinogen.
D)destroys human white cells.
E)none of the above.

Answer 2

A

Question 3

The exotoxin of Streptococcus pyogenes that causes destruction of phagocytic white cells is called

A)neurotoxin.
B)enterotoxin.
C)haemolysin.
D)leukocidin.
E)coagulase.

Answer 3

D

Question 4

Exotoxins are

A)only produced by Gram-positive bacteria.
B)highly resistant to heat.
C)released when bacterial cells die.
D)synthesised on plasmids in some bacteria.
E)proteins which damage host cells.

Question 5

The toxic shock syndrome toxin of Staphylococcus aureus

A)is a superantigen.
B)activates T lymphocytes.
C)causes a massive release of cytokines.
D)can suppress immune responses.
E)all of the above.

Question 6

Bacterial exotoxins are characteristically

A)lethal only in very large amounts.
B)proteins.
C)non-specific in their mode of action.
D)produced only by bacteria which deeply invade tissues.
E)all of the above.

Question 7

Biofilm formation may assist bacteria to

A)synchronise their toxin production.
B)attach to a surface.
C)infect a wound.
D)contaminate an intravascular catheter.
E)all of the above.

Question 8

A toxoid is

A)a type of antibody that combines with a toxin.
B)an enzyme that destroys toxins.
C)a substance produced by some bacteria.
D)an inactivated toxin used in vaccines.
E)the active substance in some drug preparations.

Question 9

The symptoms characteristic of tetanus are due to

A)the production of gas in the wound.
B)destruction of nerve cells.
C)spread of the organism through the body.
D)an exotoxin.
E)all of the above.

Question 10

The fungi that cause tinea (or ringworm)are able to infect skin because they secrete a

A)coagulase.
B)mucinase.
C)haemolysin.
D)keratinase.
E)leukocidin.

Question 11

Opportunistic pathogens

A)are able to cause disease in healthy hosts.
B)have virulence factors that overcome normal defences.
C)cause damage by releasing toxins.
D)cause disease only in hosts with weakened immune defences.
E)always cause systemic infections.

Question 12

Which of the following does NOT help bacteria to spread through body tissues?

A)Hyaluronidase.
B)Collagenase.
C)Keratinase.
D)Kinase.
E)Coagulase.

Question 13

The properties of a microorganism that enable it to cause disease are called

A)virulence factors.
B)innate factors.
C)specificities.
D)phagosomes.
E)toxoids.

Question 14

Which of the following structures does NOT assist in adherence of microorganisms to cell surfaces?

A)Adhesins.
B)Fibronectin.
C)Pili.
D)Lipopolysaccharide.
E)Glycocalyx.

Question 15

A biofilm

A)enables bacteria to move through fluids.
B)facilitates quorum sensing between bacterial cells.
C)allows host defence cells to gain access to bacteria.
D)is not normally produced in the human body.
E)is readily removed with disinfectants.

Question 16

Which of the following enzymes can be used to distinguish between different species of staphylococci?

A)Hyaluronidase.
B)Fibrinolysin.
C)Streptokinase.
D)Coagulase.
E)Haemolysin.

Question 17

Viruses can attach to target cells by

A)hooks.
B)fibronectin.
C)pili.
D)suckers.
E)envelope spikes.

Question 18

Virulent staphylococci produce an enzyme which coats the bacterial cells with fibrin and protects them against phagocytes.This enzyme is called

A)coagulase.
B)streptokinase.
C)hyaluronidase.
D)collagenase.
E)keratinase.

Question 19

The α-toxin of Staphylococcus aureus that breaks down red blood cells is a

A)neurotoxin.
B)lymphotoxin.
C)haemolysin.
D)leukocidin.
E)coagulase.

Question 20

Which of the following structures enables microbes to attach to cell surfaces?

A)Adhesins.
B)Pili.
C)Fimbriae.
D)Glycocalyx.
E)All of the above.

Question 21

Certain bacteria are able to protect themselves from phagocytosis by

A)exiting the phagosome.
B)inhibiting fusion of lysosomes with the phagosome.
C)secreting leukocidins.
D)having an antiphagocytic capsule.
E)any of the above.

Question 22

Septic shock is caused by

A)the presence of large amounts of endotoxin in the body.
B)the combined action of several neurotoxins.
C)disseminated intravascular coagulation.
D)insufficient toxoids present in the body.
E)the blockage of small blood vessels by colonies of bacteria.

Question 23

The toxin of Clostridium tetani

A)kills cells by stopping protein synthesis.
B)interferes with transmission in inhibitory neurons.
C)causes a large outflow of water and ions from intestinal epithelial cells.
D)blocks the release of acetylcholine at neuromuscular junctions.
E)kills cells by damaging the cell membrane.

Question 24

The ability of the tapeworm Echinococcus granulosis to form and reside within fluid-filled cysts inside the human body is an example of

A)antigenic shift.
B)antigenic drift.
C)concealment.
D)immunosuppression.
E)cellular transformation.

Question 25

Which of the following viruses can cause tumour formation?

A)Cutaneous wart viruses.
B)Genital wart viruses.
C)Hepatitis B virus.
D)Hepatitis C virus.
E)All of the above.

Question 26

Microorganisms can avoid body defences by

A)hiding in privileged sites.
B)repeatedly changing their surface antigens.
C)destroying some host defences.
D)remaining hidden inside host cells.
E)all of the above.

Question 27

The ability of the human immunodeficiency virus (HIV)to kill lymphocytes is an example of

A)antigenic shift.
B)antigenic drift.
C)concealment.
D)immunosuppression.
E)cellular transformation.

Question 28

The toxin of Vibrio cholerae

A)kills cells by stopping protein synthesis.
B)interferes with synaptic transmission in inhibitory interneurones.
C)causes a loss of water and ions from intestinal epithelial cells.
D)blocks the release of acetylcholine at neuromuscular junctions.
E)kills cells by damaging the cell membrane.

Question 29

The toxin produced by Vibrio cholerae

A)binds specifically to intestinal epithelial cells.
B)alters the regulatory control mechanism in the target cells.
C)causes secretion of chloride ions from the affected cells.
D)produces a watery diarrhoea.
E)all the above.

Question 30

The occurrence of minor mutations in the genes that code for the antigens of an organism is called

A)antigenic shift.
B)antigenic drift.
C)concealment.
D)antigenic switching.
E)crossing over.

Question 31

Which of the following is FALSE? Endotoxins

A)are part of the cell wall of Gram-positive bacteria.
B)may produce septic shock.
C)are a primary cause of death in meningococcal patients.
D)may cause blockage of blood vessels and tissue necrosis.
E)can cause release of pyrogens and hence fever.

Question 32

Which of the following DO NOT induce an inflammatory or immune response when infecting a person?

A)Viruses.
B)Protozoa.
C)Bacteria.
D)Prions.
E)All of the above.

Question 33

A bacterial capsule can increase an organism's virulence because it

A)breaks into fragments called endotoxins.
B)is toxic for phagocytes.
C)produces severe cytopathic effects.
D)helps the organism to evade phagocytosis.
E)specifically affects nerve cells.

Question 34

Bacterial endotoxins are

A)able to act as pyrogens.
B)part of the bacterial capsule.
C)found in Gram-positive bacteria only.
D)secreted from growing cells.
E)polypeptides.

Question 35

Influenza A virus can occasionally cause a major pandemic due to its ability to undergo

A)antigenic shift.
B)antigenic drift.
C)antigen deletion.
D)protein variation.
E)cellular transformation.