AP-Micro Microbiology: Bacteriology: Gram-Positive Identification 2

Question 1

Which enzyme produced by Staphylococcus aureus converts fibrinogen to fibrin, forming a clot around the bacteria?

Accepted Answer

Coagulase

Answer

Catalase

Answer

Urease

Answer

Hyaluronidase

Question 2

A gram-positive rod that forms a central spore and appears 'drumstick'-shaped on smear is most consistent with:

Accepted Answer

Clostridium tetani

Answer

Bacillus anthracis

Answer

Listeria monocytogenes

Answer

Clostridium perfringens

Question 3

Which characteristic distinguishes Enterococcus faecalis from Streptococcus pyogenes on laboratory media?

Accepted Answer

Growth in 6.5% NaCl broth

Answer

Beta-hemolysis on blood agar

Answer

Gram-positive cocci in chains

Answer

Catalase-negative reaction

Question 4

The CAMP test is used to presumptively identify which gram-positive organism?

Accepted Answer

Streptococcus agalactiae

Answer

Streptococcus pneumoniae

Answer

Listeria monocytogenes

Answer

Staphylococcus epidermidis

Question 5

A gram-positive coccus that is alpha-hemolytic, optochin-resistant, and bile-insoluble is most likely:

Accepted Answer

Viridans streptococci

Answer

Streptococcus pneumoniae

Answer

Enterococcus faecalis

Answer

Staphylococcus aureus

Question 6

Which gram-positive bacillus causes disease by producing a toxin that ADP-ribosylates EF-2, halting protein synthesis?

Accepted Answer

Corynebacterium diphtheriae

Answer

Bacillus cereus

Answer

Clostridium botulinum

Answer

Listeria monocytogenes

Question 7

On Mannitol Salt Agar (MSA), a yellow halo around colonies indicates:

Accepted Answer

Mannitol fermentation by S. aureus

Answer

Catalase production by S. epidermidis

Answer

Coagulase activity by S. saprophyticus

Answer

Beta-hemolysis by streptococci