Deck 17: Aerobic Gram-Positive Cocci

Question 1

The most commonly isolated gram-positive cocci are best differentiated by their

A) Gram stain morphology.
B) catalase reaction.
C) hemolytic reaction.
D) both a and b.
E) both b and c.

Answer 1

both a and b.

Question 2

The novobiocin resistance test is used to

A) determine treatment options for Staphylococcus saprophyticus.
B) identify S. saprophyticus.
C) differentiate S. saprophyticus and S. hominis ssp. novobiosepticus.
D) both a and b.

Answer 2

identify S. saprophyticus.

Question 3

The slide coagulase and the Staphylococcus latex agglutination tests are similar in that both test for the presence of

A) protein A.
B) free coagulase.
C) clumping factor.
D) thermonuclease.

Answer 3

clumping factor.

Question 4

The esculin/PYR disk test can be used to rapidly identify

A) Enterococcus spp.
B) Streptococcus pneumoniae.
C) Streptococcus pyogenes.
D) both a and b.
E) both a and c.

Question 5

The optochin disk test is incubated at/in _____________________.

A) 35°C, ambient air.
B) 35°C, CO₂.
C) 42°C, CO₂.
D) 25°C, a capnophilic atmosphere.

Question 6

A catalase-positive, gram-positive coccus that agglutinates in a slide coagulase test as well as in saline should be

A) reported as Staphylococcus aureus.
B) reported as Staphylococcus not S. aureus.
C) retested using another method.
D) retested for the catalase reaction.

Question 7

A positive rapid esculin test appears

A) dark.
B) pink.
C) red after the addition of the reagent.
D) blue.

Question 8

Yellow colonies on mannitol salt agar indicate the definitive presence of

A) methicillin-resistant Staphylococcus aureus.
B) Staphylococcus aureus.
C) Staphylococcus not S. aureus.
D) unable to definitively identify.

Question 9

A leg wound isolate presents as a yellow pigmented, beta-hemolytic, catalase-positive, gram-positive cocci in clusters. Which of the following tests would you expect to be positive for this isolate?

A) Novobiocin resistance
B) Heat-stable thermonuclease
C) PYR
D) b and c
E) a and b

Question 10

A catalase-negative coccus in pairs and short chains that is susceptible to ethyl hydrocupreine will also

A) require CO₂ for growth.
B) be alpha hemolytic.
C) be bile soluble.
D) all of the above.
E) b and c.

Question 11

The PBP2a latex agglutination test is used to detect catalase-positive, coagulase-positive, gram-positive cocci that are resistant to

A) vancomycin.
B) novobiocin.
C) oxacillin.
D) penicillin.

Question 12

A catalase-negative, gram-positive coccus in chains that is positive for esculin and PYR hydrolysis is also vancomycin resistant. What additional antibiotic resistance can this

A) high level aminoglycosides.
B) ampicillin and penicillin.
C) beta-lactamase production.
D) all of the above.
E) b and c.

Question 13

An alpha-hemolytic, catalase-negative, gram-positive coccus that is susceptible to optochin can cause all of the following diseases except

A) pneumonia.
B) sinusitis.
C) meningitis.
D) pharyngitis.

Question 14

The catalase-negative, gram-positive coccus that is the most common cause of neonatal sepsis and meningitis

A) has the potential to be vancomycin resistant.
B) hydrolyzes hippurate.
C) is susceptible to bacitracin.
D) is bile soluble.

Question 15

Necrotizing fasciitis is caused by a

A) catalase-negative, gram-positive coccus that is susceptible to bacitracin.
B) catalase-negative, gram-positive coccus that produces CAMP factor.
C) catalase-positive, gram-positive coccus that produces coagulase.
D) catalase-positive, gram-positive coccus that is resistant to novobiocin.

Question 16

Infections of indwelling devices, such as intravenous catheters, are often caused by

A) coagulase positive and thermonuclease negative.
B) coagulase negative and novobiocin resistant.
C) caogulase positive and thermonuclease positive.
D) coagulase negative and novobiocin susceptible.

Question 17

Which of the following factors accounts for the virulence of Streptococcus pyogenes?

A) "C" substance
B) Protein A
C) M protein
D) mecA gene

Question 18

The virulence factor most often associated with catalase-negative, gram-positive cocci that are bile soluble is

A) capsule production.
B) vancomycin resistance.
C) hyaluronidase.
D) streptolysin S.

Question 19

A catalase-negative, alpha-hemolytic, gram-positive coccus that is resistant to ethyl hydrocupriene is usually considered

A) a member of the normal upper respiratory flora.
B) a pathogen in an expectorated sputum specimen.
C) the causative agent of non-suppurative sequelae.
D) a common urinary pathogen.

Question 20

A catalase-positive, coagulase-negative, gram-positive coccus in clusters is isolated from the urine of a 24-year-old female. This isolate will require

A) additional testing to identify.
B) no further testing.
C) a screen for vancomycin resistance.
D) Lancefield grouping.

Question 21

A blood culture yields yellow-pigmented, beta-hemolytic, catalase-positive, gram-positive cocci in clusters. The department is out of Staphylococcus latex agglutination reagent. The microbiologist sets up a tube coagulase and mannitol salt agar. She incubates both at 35°C in CO₂ overnight. The next day the coagulase test is negative and the mannitol salt agar displays yellow colonies. How will you proceed with these results?

A) Report this organism as Staphylococcus aureus
B) Report this organism as Staphylococcus not S. aureus
C) Repeat the tests due to invalid results
D) Test the organism for novobiocin resistance

Question 22

A positive blood culture displays gram-positive cocci in chains. A sample is plated to blood, chocolate, and MacConkey agars. After 24 hours incubation in CO₂ (BA, CA) and ambient air (MAC), all agar plates show no growth. An additional test was performed and the results are provided in the image provided. Based on these results, the organism is suspicious for
Source: CDC and Dr. Mike Miller

A) viridians Streptococcus.
B) nutritionally variant Streptococcus.
C) Aerococcus spp.
D) Gemella spp.

Question 23

A patient, suspected to have bacterial endocarditis, had two sets of blood cultures drawn. All four bottles are positive with gram-positive cocci in pairs and chains. On sheep blood agar, the gray, transparent, alpha-hemolytic colonies are catalase negative, optochin resistant, ESC negative and PYR negative. Which of the following patient histories correlates with the presence of this organism?

A) 78-year-old male with bacterial pneumonia
B) 47-year-old female with a heart murmur and a history of dental surgery
C) 16-year-old female with a history of untreated pharyngitis
D) 3-day-old premature male

Question 24

A translucent colony displaying subtle beta hemolysis is isolated from a placenta culture. The Gram stain revealed gram-positive cocci in pairs. The microbiologist drops 3% catalase reagent onto a colony on sheep blood agar, and it produces bubbles. He then performs a Staphyloccocus latex agglutination and the suspension remains smooth. The next step is to

A) report the organism as Staphylococcus not S. aureus.
B) report the organism as Staphylococcus aureus.
C) repeat the catalase test due to an invalid result.
D) perform a thermonuclease test due to an invalid latex agglutination result.