Infection Biology and Diagnosis

Question 1

This is defined as a measure of a microbe’s ability to cause disease.

Answer 1

VIRULENCE

Question 2

Defined as the number of organisms required to cause disease in 50% of the population.

Answer 2

ID50

Question 3

These are inanimate objects that can harbor pathogens

Answer 3

FOMITES

Question 4

What do you call the surface proteins which mediate binding to endothelium and to extracellular proteins such as fibronectin which is presnt in SALMONELLA and E. coli?

Answer 4

CURLI proteins

Question 5

This enzyme is also known as “spreading factor”.

Answer 5

HYALURONIDASE

Question 6

Which 4 bacteria has IgA protease?

Answer 6

Strep pneumoniae, H. influenzae, Neisseria meningitidis and gonorrhoeae (these organisms live in a mucus-rich environement in the lungs and genitourinary tract where IgA is ABUNDANT so they logically need to have a protease)

Question 7

What do you call the substance produced by Staph aureus which destroys both neutrophils and macrophages?

Answer 7

Panton-Valentine Leukocidin

Question 8

Bacterial capsule prevents which host defense mechanism?

Answer 8

PHAGOCYTOSIS

Question 9

This cell wall protein of Staphylococcus aureus prevents complement activation.

Answer 9

Protein A

Question 10

All EXOTOXINS are HEAT-LABILE except?

Answer 10

Staphylococcal enterotoxin (classic example of why reheating salad would not prevent food poisoning)

Question 11

Which is the toxic comnponent of LPS which induces the overproduction of cytokines such as TNF and IL-1?

Answer 11

Lipid A

Question 12

Endotoxins can be assayed usinh which test?

Answer 12

Limulus Test

Question 13

The alpha toxin of Clostridium perfringens is called?

Answer 13

LECITHINASE

Question 14

This agar distinguishes lactose fermenters from non-lactose fermenters and H2S producers from non-producers.

Answer 14

Triple Sugar Iron (TSI)

Question 15

Which bacteria grow in TELLURITE agar?

Answer 15

Corynebacterium

Question 16

Thayer Martin Agar is used for selective growth of N. gonorrhea from NONSTERILE SITES. It is composed of which 3 antibiotics ?

Answer 16

Vancomycin (for Gram +); Colistin (for Gram -); Nystatin (for FUNGI)

Question 17

Which bacteria grow in Chocolate + Factors X and V

Answer 17

H. influenza

Question 18

Cetrimide agar is used to isolate which bacteria?

Answer 18

Pseudomonas

Question 19

Thiosulfate Citrate Bile salts (TCBS) grow which bacteria?

Answer 19

Vibrio cholerae (Think TCVS instead)

Question 20

Which bacteria grow in Eaton? XLD? Charcoal yeast? Skirrows? BSK? Bordet-Gengou/Regan Lowe?

Answer 20

Eaton = Mycoplasma pneumoniae; XLD = Salmonella’ Shigella; Charcoal yeast = Legionella; Skirrows = Campylobacter, Helicobacter; BSK = Borrelia burgdorferi; Bordet-Gengou = Bordetella

Question 21

Fletcher’s agar or EMJH grow which organism?

Answer 21

Leptospira interrogans

Question 22

Which gene confers resistance to methicillin?

Answer 22

mec gene found in MRSA