ASCP Microbiology 1

Question 1

Which organism is the most common cause of community-acquired urinary tract infections?

Accepted Answer

Escherichia coli

Answer

Escherichia coli accounts for approximately 80–85% of community-acquired urinary tract infections.

Question 2

A Gram stain showing gram-positive cocci in clusters is most consistent with:

Accepted Answer

Staphylococcus species

Answer

Staphylococci characteristically appear as gram-positive cocci in grape-like clusters on Gram stain.

Question 3

Which test differentiates Staphylococcus aureus from coagulase-negative staphylococci?

Accepted Answer

Coagulase test

Answer

S. aureus produces coagulase, which clots plasma, while coagulase-negative staphylococci (e.g., S. epidermidis) do not.

Question 4

Which medium is selective for gram-negative enteric pathogens like Salmonella and Shigella?

Accepted Answer

Hektoen enteric (HE) agar

Answer

Hektoen enteric agar inhibits gram-positive bacteria and differentiates enteric pathogens by lactose fermentation and H2S production.

Question 5

The CAMP test is used to identify which organism?

Accepted Answer

Streptococcus agalactiae (Group B Strep)

Answer

Group B Streptococcus produces the CAMP factor that enhances beta-hemolysis of S. aureus, creating an arrowhead zone.

ASCP Practice Test