Deck 13: Staphylococcus Micrococcus and Similar Organisms

Question 1

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

A) clumping factor.
B) free coagulase.
C) extracellular coagulase.
D) catalase.

Answer 1

A
The rapid slide test is a screening test for one form of coagulase produced by Staphylococcus aureus that is positive for 90% of all isolates of this organism.

Question 2

Isolates of coagulase-negative Staphylococcus from urinary tract infections can be presumptively identified as S.saprophyticus on the basis of its:

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

Answer 2

B
Novobiocin resistance is a unique trait of S.saprophyticus, and testing for this trait is commonly used to identify this bacterium in the clinical setting.

Question 3

Which group of bacteria is described as catalase positive and is gram-positive cocci that grow facultatively anaerobic and form grapelike clusters?

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

Answer 3

C
All descriptions given are those of the Staphylococcus species.

Question 4

The resident human flora, staphylococcus, which is more likely to cause infections in compromised hosts such as patients with cancer, is:

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

Question 5

The tube coagulase test:

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

Question 6

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 7

The species of Staphylococcus, which is one of the most important human pathogens, is:

A) S. lentus.
B) S. aureus.
C) S. mucilaginosus.
D) S. intermedius.

Question 8

An infected intravenous (IV)catheter tip grew out gram-positive cocci, which were catalase positive and coagulase negative.The zone size of the novobiocin disk measured 18 mm.The most likely organism causing infection is:

A) Staphylococcus saprophyticus.
B) S. epidermidis.
C) S. hominis.
D) S. cohnii.

Question 9

The most frequent agent of nosocomial bacteremia is:

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

Question 10

Which 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 11

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

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

Question 12

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

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

Question 13

Which organism is catalase positive, coagulase negative, pyrrolidonyl arylamidase (PYR)positive, susceptible to novobiocin, urease negative, and beta hemolytic on sheep blood agar?

A) Staphylococcus epidermidis
B) S. saprophyticus
C) S. cohnii
D) S. haemolyticus

Question 14

A tube coagulase test was performed on catalase-positive, gram-positive cocci that were beta hemolytic and grew on mannitol salt agar.The tube was checked after overnight incubation and was negative.Which of the following statements explains this discrepancy?

A) A tube coagulase should not be performed on a catalase-positive organism.
B) A beta-hemolytic colony, which is catalase positive and grows on mannitol salt, is normally coagulase negative.
C) The test should have been read in 1 to 4 hours in case any hemolysins are present.
D) No discrepancy is present; the results are accurate.

Question 15

Quality control should be performed on which two organisms to determine the validity of the oxidase reagent?

A) Staphylococcus aureus and S. epidermidis
B) S. epidermidis and Enterococcus
C) Aerococcus and Enterococcus
D) Micrococcus and Aerococcus