CMLA Microbiology Basics 4

Question 1

The coagulase test is used primarily to identify which pathogen?

Accepted Answer

Staphylococcus aureus

Answer

Staphylococcus aureus is coagulase-positive, clotting plasma by converting fibrinogen to fibrin, which distinguishes it from coagulase-negative staphylococci like S. epidermidis.

Question 2

Which culture medium is used for the primary isolation of Neisseria gonorrhoeae?

Accepted Answer

Thayer-Martin agar

Answer

Thayer-Martin agar is a modified chocolate agar with antibiotics (VCN: vancomycin, colistin, nystatin) that selectively isolates Neisseria gonorrhoeae from genital specimens.

Question 3

A spore-forming, Gram-positive rod that causes food poisoning via a heat-stable enterotoxin is:

Accepted Answer

Bacillus cereus

Answer

Bacillus cereus produces a heat-stable emetic toxin associated with reheated rice and a heat-labile diarrheal toxin; it forms spores allowing survival of cooking.

Question 4

The KOH (potassium hydroxide) preparation is used in microbiology to:

Accepted Answer

Clear debris and visualize fungal elements

Answer

KOH dissolves keratin and cellular debris in skin, nail, or hair samples, allowing fungal hyphae and spores to be seen clearly under microscopy.

Question 5

Which test confirms that an isolate ferments lactose on MacConkey agar by producing a pink/red colony?

Accepted Answer

The organism is a lactose fermenter producing acid

Answer

MacConkey agar contains lactose and neutral red dye; lactose-fermenting organisms produce acid that turns the pH indicator, making colonies appear pink to red.

(CMLA) Certified Medical Laboratory Assistant Practice Test

(CMLA) Certified Medical Laboratory Assistant Practice Test

CMLA Microbiology Basics 4