Deck 13: Staphylococcus, Micrococcus, and Similar Organisms

Question 1

The most frequent agent of nosocomial bacteremia is

A)catalase-negative micrococci.
B)coagulase-positive staphylococci.
C)catalase-negative stomatococci.
D)coagulase-negative staphylococci.

Answer 1

D
The coagulase-negative staphylococci, among which S. epidermidis is the most commonly encountered, are opportunistic pathogens and their prevalence as nosocomial pathogens is highly related to medical procedures and practices.

Question 2

The staphylococcus that is more likely to cause uncomplicated urinary tract infections in nonhospitalized hosts, especially sexually active young women, is

A)Staphylococcus saprophyticus.
B)Staphylococcus aureus.
C)Staphylococcus epidermidis.
D)Staphylococcus intermedius.

Answer 2

A
Staphylococcus saprophyticus is most frequently associated with community-acquired urinary tract infections in young, sexually active females but is not commonly associated with hospital-acquired infections or any infections at nonurinary tract sites.

Question 3

The tube coagulase test

A)detects bound coagulase.
B)detects extracellular coagulase.
C)is performed on slide coagulase-positive isolates to confirm this positive result.
D)requires citrated reagent plasma.

Answer 3

B
The tube coagulase test is a test for the form of coagulase produced by Staphylococcus aureus that is called extracellular coagulase.

Question 4

In clinical isolates, the most likely identification of a coagulase-positive, catalase-positive, gram-positive cocci that is penicillin-resistant would be

A)Staphylococcus aureus.
B)Staphylococcus intermedius.
C)Stomatococcus luteus.
D)Micrococcus aureus.

Question 5

The slide coagulase test is a rapid screening test for the production of

A)clumping factor.
B)free coagulase.
C)extracellular coagulase.
D)catalase.
E)All of the above are correct.

Question 6

The species of Staphylococcus that is one of the most important human pathogens is

A)Staphylococcus luteus.
B)Staphylococcus aureus.
C)Staphylococcus mucilaginosus.
D)Staphylococcus intermedius.

Question 7

The first identification test performed on a clinical isolate of gram-positive, catalase-positive cocci would likely be the

A)penicillin test.
B)Gram stain.
C)oxidase test.
D)coagulase test.

Question 8

Isolates of coagulase-negative Staphylococcus from urinary tract infections can be presumptively identified as S.saprophyticus based on

A)penicillin susceptibility.
B)novobiocin resistance.
C)penicillin resistance.
D)novobiocin susceptibility.

Question 9

This virulent and important human pathogen can also be recovered from the nares, perineum, and other skin sites of healthy people, especially in the hospital setting.

A)Micrococcus luteus
B)Staphylococcus intermedius
C)Staphylococcus aureus
D)All Micrococcaceae

Question 10

Choose the group of bacteria that is described as catalase-positive, gram-positive cocci that grow facultatively anaerobic and that form grapelike clusters.

A)Neisseria
B)Rothia (stomatococci)
C)Staphylococcus
D)Micrococcus

Question 11

The purpose of the coagulase test is to

A)detect the presence of an enzyme that binds plasma fibrinogen.
B)detect the ability of the organism to clot plasma.
C)detect the production of clumping factor.
D)help identify staphylococci.
E)All of the above are correct.

Question 12

The resident human flora staphylococcus that is more likely to cause infections in compromised hosts such as cancer patients is

A)Staphylococcus saprophyticus.
B)Staphylococcus aureus.
C)Staphylococcus epidermidis.
D)Staphylococcus intermedius.