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Harr Micro > Micro 8.5 Gram-Positive and Gram-Negative Cocci > Flashcards

Micro 8.5 Gram-Positive and Gram-Negative Cocci Flashcards

1
Q
  1. The test used most often to separate Staphylococcus and Micrococcus spp. from Streptococcus spp. is:

A. Bacitracin
B. Catalase
C. Hemolysis pattern
D. All of these options

A

B. Catalase

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2
Q
  1. Micrococcus and Staphylococcus spp. are differentiated by which test(s)?

A. Fermentation of glucose (OF tube)
B. Catalase test
C. Gram stain
D. All of these options

A

A. Fermentation of glucose (OF tube)

Both micrococci and staphylococci are catalase-positive and gram-positive cocci. On direct smears, they both appear as pairs, short chains (resembling Streptococcus spp.), or clusters. However, the micrococci fail to produce acid from glucose under anaerobic conditions. For OF tube reactions:
Staphylococcus spp. is positive for both open tube (oxidation) and closed tube (fermentation)
Micrococcus spp. is positive for open tube but negative for closed tube

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3
Q
  1. Lysostaphin is used to differentiate Staphylococcus from which other gram-positive, catalase-positive organisms?

A. Streptococcus
B. Aerococcus
C. Micrococcus
D. Enterococcus

A

C. Micrococcus

Lysostaphin is an endopeptidase that cleaves the glycine-rich pentapeptide cross-bridges in the staphylococcal cell wall peptidoglycan. The susceptibility of the staphylococci to lysostaphin (less than 200 μg/mL) is used to differentiate them from the micrococci. Staphylococci are susceptible and show a 10- to 16-mm zone of inhibition, whereas micrococci are not inhibited and will grow up to the disk.

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4
Q
  1. Which of the following tests is used routinely to identify S. aureus?

A. Slide coagulase test
B. Tube coagulase test
C. Latex agglutination
D. All of these options

A

D. All of these options

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5
Q
  1. Which of the following enzymes contribute to the virulence of S. aureus?

A. Urease and lecithinase
B. Hyaluronidase and β-lactamase
C. Lecithinase and catalase
D. Cytochrome oxidase

A

B. Hyaluronidase and β-lactamase

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6
Q
  1. Toxic shock syndrome is attributed to infection with:

A. Staphylococcus epidermidis
B. Staphylococcus hominis
C. Staphylococcus aureus
D. Staphylococcus saprophyticus

A

C. Staphylococcus aureus

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7
Q
  1. Which Staphylococcus species, in addition to S. aureus, also produces coagulase using the tube coagulase test?

A. Staphylococcus intermedius
B. Staphylococcus saprophyticus
C. Staphylococcus hominis
D. Staphylococcus haemolyticus

A

A. Staphylococcus intermedius

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8
Q

S. epidermidis (coagulase negative) is recovered from which of the following sources?

A. Prosthetic heart valves
B. Intravenous catheters
C. Urinary tract
D. All of the above

A

D. All of the above

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9
Q
  1. Slime production is associated with which Staphylococcus species?

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

A

B. Staphylococcus epidermidis

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10
Q
  1. Strains of Staphylococcus species resistant to the β-lactam antibiotics by standardized disk diffusion and broth microdilution susceptibility methods are called:

A. Heteroresistant
B. Bacteriophage group 52A
C. Cross-resistant
D. Plasmid-altered

A

A. Heteroresistant

Methicillin-resistant S. aureus (MRSA) and methicillin-resistant S. epidermidis (MRSE) are called heteroresistant.

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11
Q
  1. S. saprophyticus is best differentiated from S. epidermidis by its resistance to:

A. 5 µg of lysostaphin
B. 5 µg of novobiocin
C. 10 units of penicillin
D. 0.04 unit of bacitracin

A

B. 5 µg of novobiocin

S. saprophyticus is coagulase negative and resistant to 5 µg of novobiocin. When using the standardized Kirby-Bauer sensitivity procedure, a 6- to 12-mm zone of growth inhibition is considered resistant. Susceptible strains measure 16 to 27 mm (inhibition) zones.

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12
Q
  1. The following results were observed by using a tube coagulase test:
    Coagulase at 4 hours = +
    Coagulase at 18 hours = Neg
    DNase = +
    Novobiocin = Sensitive (16-mm zone)
    Hemolysis on blood agar = β
    Mannitol salt plate = + (acid production)
    What is the most probable identification?

A. Staphylococcus saprophyticus
B. Staphylococcus epidermidis
C. Staphylococcus aureus
D. Staphylococcus hominis

A

C. Staphylococcus aureus

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13
Q
  1. S. aureus recovered from a wound culture gave the following antibiotic sensitivity pattern by the standardized Kirby-Bauer method (S = sensitive; R = resistant):
    Penicillin = R
    Cephalothin = R
    Vancomycin = S
    Ampicillin = S
    Cefoxitin = R
    Methicillin = R
    Which is the drug of choice for treating this infection?

A. Penicillin
B. Ampicillin
C. Cephalothin
D. Vancomycin

A

D. Vancomycin

Vancomycin, along with rifampin, is used for strains of S. aureus that are resistant to the β-lactams. MRSA strains pose problems when reading the zone sizes for these strains. Their heteroresistance results in a film of growth consisting of very small colonies formed within the defined inhibition zone surrounding the antibiotic disk. Initially, this appears as a mixed culture or contaminant.

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14
Q
  1. Which of the following tests should be used to following a coagulase-positive tube test (free coagulase) to separate S. aureus from S. intermedius? The culture specimen was obtained from a patient who suffered a dog-bite wound.

A. Acetoin
B. Catalase
C. Slide coagulase
D. Urease

A

A. Acetoin

The production of acetoin by S. aureus from glucose or pyruvate differentiates it from S. intermedius, which is also coagulase positive (positive for clumping factor and free coagulase or tube test). This test is the Voges-Proskauer (VP) test. Acetoin production is detected by addition of 40% KOH and 1% α-naphthol to the VP test broth after 48 hours of incubation. A distinct pink color within 10 minutes denotes a positive test result.

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15
Q
  1. A gram-positive coccus recovered from a wound ulcer from a 31-year-old patient with
    diabetes showed pale yellow, creamy, β-hemolytic colonies on blood agar. Given the
    following test results, what is the most likely identification?
    Catalase = +
    Glucose OF: Positive open tube, negative sealed tube
    Mannitol salt = Neg
    Slide coagulase = Neg

A. Staphylococcus aureus
B. Staphylococcus epidermidis
C. Micrococcus spp.
D. Streptococcus spp.

A

C. Micrococcus spp.

Micrococcus spp. utilize glucose oxidatively but not under anaerobic conditions (sealed tube). Staphylococcus spp. utilize glucose oxidatively and anaerobically. The catalase differentiates the Micrococcaceae family (positive) from the Streptococcaceae family (negative).

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16
Q
  1. Urine cultured from the catheter of an 18-year-old female patient produced more than 100,000 col/mL on a CNA plate. Colonies were catalase positive, coagulase negative by the latex agglutination slide method as well as the tube coagulase test. The best single test for identification is:

A. Lactose fermentation
B. Urease
C. Catalase
D. Novobiocin susceptibility

A

D. Novobiocin susceptibility

S. epidermidis and S. saprophyticus are the two possibilities because they are both catalase positive, coagulase negative, urease positive, and ferment lactose. Novobiocin susceptibility is the test of choice for differentiating these two species. S. epidermidis is sensitive, but S. saprophyticus is resistant to 5 μg of novobiocin. UTIs caused by S. saprophyticus are often seen in cultures from sexually active young females.

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17
Q
  1. A Staphylococcus spp. recovered from a wound (cellulitis) was negative for the slide coagulase test (clumping factor) and negative for novobiocin resistance. The next test(s) needed for identification is (are):

A. Tube coagulase test
B. β-Hemolysis on blood agar
C. Mannitol salt agar plate
D. All of these options

A

D. All of these options

S. aureus is novobiocin sensitive and cannot be ruled out by a negative clumping factor test. Most S. aureus produce β-hemolysis on sheep blood agar plates and are mannitol salt positive (produce acid and are not inhibited by the high salt concentration). The tube test (to detect free coagulase) should be performed because the slide test was negative.

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18
Q
  1. Furazolidone (Furoxone) susceptibility is a test used to differentiate:

A. Staphylococcus spp. from Micrococcus spp.
B. Streptococcus spp. from Staphylococcus spp.
C. Staphylococcus spp. from Pseudomonas spp.
D. Streptococcus spp. from Micrococcus spp.

A

A. Staphylococcus spp. from Micrococcus spp.

Staphylococci are susceptible to furazolidone, giving zones of inhibition that are 15mm or greater. Micrococcus spp. are resistant to furazolidone, giving zones of 6 to 9mm. The test is performed as a disk susceptibility procedure using a blood agar plate.

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19
Q
  1. Bacitracin resistance (0.04 unit) is used to differentiate:

A. Micrococcus spp. from Staphylococcus spp.
B. Staphylococcus spp. from Neisseria spp.
C. Planococcus spp. from Micrococcus spp.
D. Staphylococcus spp. from Streptococcus spp.

A

A. Micrococcus spp. from Staphylococcus spp.

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20
Q
  1. Which of the following tests will rapidly differentiate micrococci from staphylococci?

A. Catalase
B. Coagulase
C. Modified oxidase
D. Novobiocin susceptibility

A

C. Modified oxidase

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21
Q
  1. Streptococcus species exhibit which of the following properties?

A. Aerobic, oxidase positive, and catalase positive
B. Facultative anaerobic, oxidase negative, catalase negative
C. Facultative anaerobic, β-hemolytic, catalase positive
D. May be α-, β-, or γ-hemolytic, catalase positive

A

B. Facultative anaerobic, oxidase negative, catalase negative

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22
Q
  1. Which group of β-hemolytic streptococci is associated with erythrogenic toxin production?

A. Group A
B. Group B
C. Group C
D. Group G

A

A. Group A

Group A β-hemolytic streptococci are the cause of scarlet fever, and some strains produce toxins (pyrogenic exotoxins A, B, and C) that cause a scarlatiniform rash. Streptococcus pyogenes is the cause of puerperal fever, streptococcal toxic shock, rheumatic fever, and a severe “flesh-eating” bacterial infection.

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23
Q
  1. A fourfold rise in titer of which antibody is the best indicator of a recent infection with group A β-hemolytic streptococci?

A. Anti-streptolysin O
B. Anti-streptolysin S
C. Anti-A
D. Anti-B

A

A. Anti-streptolysin O

The antistreptolysin O (ASO) titer is used to indicate a recent infection with group A β-hemolytic streptococci. Streptolysin O may also be produced by some strains of groups C and G streptococci.

24
Q
  1. The L-pyrrolidonyl-β-napthylamide (PYR), hippurate, and CAMP tests can be used for the presumptive identification of which group of β-hemolytic streptococci?

A. Groups A and B
B. Groups C and D
C. Group C
D. Group F

A

A. Groups A and B

The bacitracin A disk test is no longer used, but the PYR, hippurate hydrolysis, and CAMP tests are used for the presumptive identification of the β-hemolytic streptococci. In addition to group A, groups C, F, and G are also β-hemolytic and give a positive test result for bacitracin (a zone of inhibition of any size). Therefore, a positive bacitracin A disc test does not confirm the presence of group A β-hemolytic streptococci. Group A strep test positive for PYR but negative for hippurate and the CAMP test. Group B streptococci test negative in the PYR test but positive in the hippurate and CAMP tests. Groups C, G and F test negative in all three tests.

25
Q
  1. To diagnose streptococcal pharyngitis, primary plates of blood agar and blood agar with sulfamethoxazole-trimethoprim (SXT) are used to differentiate which streptococci?

A. α-Hemolytic streptococci
B. β-Hemolytic streptococci
C. Streptococcus pneumoniae
D. Enterococcus faecalis

A

B. β-Hemolytic streptococci

SXT is inhibitory to most streptococci except S. pyogenes and Streptococcus agalactiae. For this reason, SXT is used in a commercially available streptococcal selective agar (SSA) as a primary plating agar for the detection of group A streptococci. Latex agglutination test kits are used for the rapid detection of β-
hemolytic streptococci Lancefield groups A, B, C, F, and G.

26
Q
  1. β-Hemolytic streptococci, not of group A or B, usually exhibit which of the following reactions?

A. Bacitracin: Susceptible, Sulfamethoxazole-Trimethoprim: Resistant
B. Bacitracin: Resistant, Sulfamethoxazole-Trimethoprim: Resistant
C. Bacitracin: Resistant, Sulfamethoxazole-Trimethoprim: Susceptible
D. Bacitracin: Susceptible or resistant, Sulfamethoxazole-Trimethoprim: Susceptible

A

D. Bacitracin: Susceptible or resistant, Sulfamethoxazole-Trimethoprim: Susceptible

27
Q
  1. A false-positive CAMP test result for the presumptive identification of group B streptococci may occur if the plate is incubated in a(n):

A. Candle jar or CO2 incubator
B. Ambient air incubator
C. 35°C incubator
D. 37°C incubator

A

A. Candle jar or CO2 incubator

The CAMP test (described by Christie, Atkins, and Munch-Petersen in 1944) refers to a hemolytic interaction (flaming arrowhead) that is seen on a blood agar plate between the β-hemolysins produced by most strains of S. aureus and an extracellular protein produced by both hemolytic and nonhemolytic isolates of group B streptococci. In a CAMP test, the plate must be placed in an ambient air incubator at 35°C to 37°C. Group A streptococci may be CAMP positive if the plate is incubated in a candle jar, high CO2 atmosphere, or anaerobically.

28
Q
  1. Which test is used to differentiate α-hemolytic streptococci from the Enterococcus spp. and S. bovis growing on blood agar?

A. Bacitracin disk test
B. CAMP test
C. Hippurate hydrolysis test
D. Bile esculin test

A

D. Bile esculin test

The bile esculin test differentiates those bacteria that can hydrolyze esculin and also grow in the presence of 4% bile salts or 40% bile. The bile esculin slant or plate is inoculated on the surface and incubated for 24 to 48 hours in a non-CO2 incubator. Group D streptococci (enterococci and nonenterococci) are positive, causing blackening of half or more of the slant within 48 hours. Viridans streptococci are negative (do not grow or hydrolyze esculin).

29
Q
  1. The bile solubility test causes the lysis of:

A. Streptococcus bovis colonies on a blood agar plate
B. Streptococcus pneumoniae colonies on a blood agar plate
C. Group A streptococci in broth culture
D. Group B streptococci in broth culture

A

B. Streptococcus pneumoniae colonies on a blood agar plate

The bile solubility test can be performed directly by dropping 2% sodium deoxycholate onto a few well-isolated colonies of S. pneumoniae. The bile salts speed up the autolysis observed in pneumococcal cultures. The colonies lyse and disappear when incubated at 35°C for 30 minutes, leaving a partially hemolyzed area on the plate. The same phenomenon can be seen using a broth culture; addition of 10% deoxycholate to broth containing S. pneumoniae results in visible clearing of the suspension after incubation at 35°C for 3 hours.

30
Q
  1. S. pneumoniae and the α-hemolytic viridans streptococci can be differentiated by which test?

A. Optochin P disk test, 5 µg/mL or less
B. Bacitracin A disk test, 0.04 unit
C. CAMP test
D. Bile esculin test

A

A. Optochin P disk test, 5 µg/mL or less

Optochin (P disk) at a concentration of 5 μg/mL or less inhibits the growth of S. pneumoniae but not viridans streptococci. However, optochin at a concentration in excess of 5 μg/mL inhibits viridans streptococci as well if incubated under 5% CO2 at 35°C for 18 to 24 hours. A zone of inhibition of 14 mm or more around the 6-mm disk is considered a presumptive identification of S. pneumoniae. A questionable zone size should be confirmed by performing a bile solubility test.

31
Q
  1. The salt tolerance test (6.5% salt broth) is used to presumptively identify:

A. Streptococcus pneumoniae
B. Streptococcus bovis
C. Viridans streptococci
D. Enterococcus faecalis

A

D. Enterococcus faecalis

E. faecalis will grow in 6.5% salt, and the nonenterococci (S. bovis and S. equinus) will not. This test distinguishes the enterococci group from S. bovis and S. equinus (nonenterococci group). Both groups grow on bile esculin agar. Viridans streptococci are negative for 6.5% salt growth and will not grow on bile esculin agar.

32
Q
  1. In addition to E. faecalis, which other streptococci will grow in 6.5% salt broth?

A. Group A streptococci
B. Group B streptococci
C. Streptococcus pneumoniae
D. Streptococcus bovis

A

B. Group B streptococci

33
Q
  1. A spinal fluid specimen and blood cultures were obtained from a 1-year-old infant with a respiratory infection. Growth on blood agar showed nonhemolytic, streptococci. The Quellung test is used to identify which of the following Streptococcus species?

A. Streptococcus pyogenes
B. Streptococcus agalactiae
C. Viridans streptococci
D. Streptococcus pneumoniae

A

D. Streptococcus pneumoniae

A precipitin reaction seen microscopically with methylene blue stain (microprecipitin reaction) occurs between the carbohydrate of the capsule of S. pneumoniae and anticapsular antibody. The antibody may be type specific or polyvalent. Binding of antibodies to the bacteria causes the capsule to swell, identifying the organisms as S. pneumoniae. Antigen detection kits are used to identify S. pneumoniae recovered from CSF and blood cultures. S. pneumoniae is the cause of 95% of the bacterial pneumonias in unvaccinated children and the leading cause of bacterial meningitis.

34
Q
  1. The PYR hydrolysis test is a presumptive test for which group of β-hemolytic streptococci?

A. Group A and Enterococcus
B. Group A and B β-hemolytic streptococci
C. Non–group A or non–group B β-hemolytic streptococci
D. Streptococcus pneumoniae and Streptococcus bovis

A

A. Group A and Enterococcus

The PYR hydrolysis test is highly specific for group A streptococci and Enterococcus spp. The test detects the pyrrolidonylarylamidase enzyme, which hydrolyzes PYR

35
Q
  1. A pure culture of β-hemolytic streptococci recovered from a leg wound ulcer gave the following reactions:
    CAMP test = Neg
    Bile esculin = Neg
    Hippurate hydrolysis = Neg
    6.5% salt = Neg
    PYR = Neg
    Optochin = Resistant
    Bacitracin = Resistant
    SXT = Sensitive
    The most likely identification is:

A. Group A streptococci
B. Group B streptococci
C. Enterococcus spp.
D. Non–group A, non–group B streptococci

A

D. Non–group A, non–group B streptococci

36
Q
  1. β-Hemolytic streptococci, greater than 50,000 col/mL, were isolated from a urinary tract catheter urine specimen. Given the following reactions, what is the most likely identification?
    CAMP test = Neg
    Bile solubility = Neg
    PYR = +
    SXT = Resistant
    Optochin = Resistant
    Hippurate hydrolysis = ±
    6.5% salt = +
    Bile esculin = +
    Bacitracin = Resistant
    Vancomycin = Resistant

A. Group A streptococci
B. Group B streptococci
C. Enterococcus faecalis, Enterococcus faecium
D. Non–group A, non–group B streptococci

A

C. Enterococcus faecalis, Enterococcus faecium

VRE (Vancomycin-Resistant Enterococcus) denotes E. faecalis and Enterococcus facium, which have shown resistance to most antimicrobials used to treat infections caused by gram-positive cocci (ampicillin, methicillin and other β-lactams) and therefore have mutated and now are resistant to vancomycin. Group A streptococci are sensitive to bacitracin and negative for bile esculin and 6.5% salt broth. Group B streptococci will grow in 6.5% salt broth but are negative for bile esculin and PYR. The non–group A, non–group B streptococci will not grow in 6.5% salt broth and are sensitive to SXT. E. faecalis is positive for bile esculin, 6.5% salt broth, and PYR.

37
Q
  1. Abiotrophia spp. or nutritionally variant streptococci (NVS) require specific thiol compounds, cysteine, or the active form (pyridoxal) of vitamin B6. Which of the following tests supplies these requirements for growth?

A. CAMP test
B. Bacitracin susceptibility test
C. Bile solubility test
D. Staphylococcal cross-streak test

A

D. Staphylococcal cross-streak test

The staphylococcal streak, across the NVS inoculum, provides the nutrients needed. Very small colonies of NVS can be seen growing adjacent to the staphylococcal streak on the blood agar plate in a manner similar to the satellite phenomenon of Haemophilus spp. around S. aureus. NVS are normal flora of the oral cavity but may cause life-threatening infections when introduced into sterile areas (cause of endocarditis). Blood culture media will supply the necessary nutrients for their recovery.

38
Q
  1. Many β-hemolytic streptococci recovered from a wound were found to be penicillin resistant. Given the following results, what is the most likely identification?
    Bile esculin = +
    PYR = +
    6.5% salt = +
    Hippurate hydrolysis = +
    SXT = Resistant
    Bile solubility = Neg

A. Enterococcus faecalis
B. Streptococcus pneumoniae
C. Streptococcus bovis
D. Group B streptococci

A

A. Enterococcus faecalis

E. faecalis is resistant to penicillin and ampicillin as well as some of the aminoglycoside antibiotics. Pneumococci, group B streptococci, and S. bovis are PYR negative.

39
Q
  1. Which two tests best differentiate α-hemolytic S. bovis from Streptococcus salivarius which is also α-hemolytic?

A. Bile esculin and 6.5% salt broth
B. Starch hydrolysis and acid production from mannitol
C. Bacitracin and PYR
D. SXT susceptibility and PYR

A

B. Starch hydrolysis and acid production from mannitol

S. bovis and S. salivarius are physiologically and biochemically similar. They are both PYR and 6.5% salt broth negative and bile esculin positive, but only S. bovis is positive for mannitol and starch reactions.

40
Q
  1. Two blood cultures obtained from a newborn grew β-hemolytic streptococci with the following reactions:
    CAMP test = +
    Bile solubility = Neg
    Bacitracin = Resistant
    Hippurate hydrolysis = +
    6.5% salt = +
    Bile esculin = Neg
    PYR = Neg
    SXT = Resistant
    Which is the most likely identification?

A. Group A streptococci
B. Group B streptococci
C. Enterococcus faecalis
D. Non–group A, non–group B streptococci

A

B. Group B streptococci

Group B streptococci (S. agalactiae) are resistant to both bacitracin and SXT. Unlike group A and E. faecalis, the group B streptococci are negative for PYR. With some exceptions, group B streptococci will grow in 6.5% salt broth. Group B strep infections in newborns are the result of premature rupture of the mother’s membranes. The infection in a newborn happens within the first 5 days after birth and results in fever, sepsis, meningitis, and respiratory distress.

41
Q
  1. MTM medium is used primarily for the selective recovery of which pathogenic Neisseria spp. organism from genital specimens?

A. Neisseria gonorrhoeae
B. Neisseria lactamica
C. Neisseria sicca
D. Neisseria flavescens

A

A. Neisseria gonorrhoeae

42
Q
  1. Variation in colony types seen with fresh isolates of N. gonorrhoeae and sometimes with N. meningitidis are the result of:

A. Multiple nutritional requirements
B. Pili on the cell surface
C. Use of a transparent medium
D. All of these options

A

D. All of these options

43
Q
  1. Gram-negative diplococci recovered from an MTM plate and giving a positive oxidase test result can be presumptively identified as:

A. Neisseria gonorrhoeae
B. Neisseria meningitidis
C. Neisseria lactamica
D. All of these options

A

D. All of these options

44
Q
  1. Colonies growing on MTM and showing a 4+ reaction with the Superoxol test may be considered as a rapid presumptive test for:

A. Neisseria gonorrhoeae
B. Neisseria meningitidis
C. Neisseria lactamica
D. Moraxella (Branhamella) catarrhalis

A

A. Neisseria gonorrhoeae

45
Q
  1. Nonpathogenic Moraxella spp. capable of growing on selective media for Neisseria can best be differentiated from pathogenic Neisseria spp. by which test?

A. Catalase test
B. 10-unit penicillin disk on blood agar
C. Oxidase test
D. Superoxol test

A

B. 10-unit penicillin disk on blood agar

46
Q
  1. A Gram stain of a urethral discharge from a man showing extracellular and intracellular gram-negative diplococci within segmented neutrophils is a presumptive identification for:

A. Neisseria gonorrhoeae
B. Neisseria meningitidis
C. Moraxella (Branhamella) catarrhalis
D. Neisseria lactamica

A

A. Neisseria gonorrhoeae

47
Q
  1. The β-galactosidase test aids in the identification of which Neisseria species?

A. Neisseria lactamica
B. Neisseria meningitidis
C. Neisseria gonorrhoeae
D. Neisseria flavescens

A

A. Neisseria lactamica

48
Q
  1. Cystine tryptic digest (CTA) media used for identification of Neisseria spp. should be inoculated and cultured in:

A. A CO2 incubator at 35°C for 24 hours
B. A CO2 incubator at 42°C for up to 72 hours
C. A non-CO2 incubator at 35°C for up to 72 hours
D. An anaerobic incubator at 35°C for up to 72 hours

A

C. A non-CO2 incubator at 35°C for up to 72 hours

49
Q
  1. Culture on MTM media of a vaginal swab produced several colonies of gram-negative
    diplococci that were catalase and oxidase positive and Superoxol negative. Given the following carbohydrate reactions, select the most likely identification.
    Glucose = +
    Sucrose = Neg
    Lactose = +
    Maltose = +
    Fructose = Neg

A. Neisseria gonorrhoeae
B. Neisseria sicca
C. Neisseria flavescens
D. Neisseria lactamica

A

D. Neisseria lactamica

50
Q
  1. Sputum from a patient with pneumonia produced many colonies of gram-negative diplococci on a chocolate plate that were also present in fewer numbers on MTM after 48 hours. Given the following results, what is the most likely identification?
    Catalase = +
    DNase = +
    Glucose = Neg
    Lactose = Neg
    Fructose = Neg
    Oxidase = +
    Tributyrin hydrolysis = +
    Sucrose = Neg
    Maltose = Neg

A. Moraxella catarrhalis
B. Neisseria flavescens
C. Neisseria sicca
D. Neisseria elongata

A

A. Moraxella catarrhalis

51
Q
  1. Showing resistance to which drug categorizes a strain of S. aureus as MRSA?

A. Oxacillin
B. Colistin
C. Sulfamethoxazole-Trimethoprim
D. Tetracycline

A

A. Oxacillin

52
Q
  1. An oxacillin-disk screen test is used to detect S. pneumoniae resistance to penicillin. Using Mueller-Hinton agar with 5% sheep blood and a 1-µg oxacillin disk, what is the recommended inhibition zone size for penicillin susceptibility?

A. 5 mm or greater
B. 10 mm or greater
C. 15 mm or greater
D. 20 mm or greater

A

D. 20 mm or greater

53
Q
  1. Which one of the following organisms is a known producer of β-lactamase–producing strains, and should be tested (screened) by a commercial β-lactamase assay prior to susceptibility testing?

A. Streptococcus pneumoniae
B. Group B streptococci
C. Enterococcus spp.
D. Planococcus spp.

A

C. Enterococcus spp.

54
Q
  1. Which test is used for the determination of inducible clindamycin resistance in staphylococci and streptococci?

A. E-test
B. D-zone test
C. A-test
D. CAMP test

A

B. D-zone test

55
Q
  1. A wound specimen was obtained from an older patient with diabetes and identified as being positive for vancomycin-resistant S. aureus (VRSA). The method used to determine VRSA was the standard microdilution technique. To be considered VSRA positive, which MIC must have been reported?

A. MIC 16µg/mL or greater
B. MIC of 8 to 16 µg/mL
C. MIC of 4 to 8 µg/mL
D. MIC 8 µg/mL or greater

A

A. MIC 16µg/mL or greater

56
Q
  1. “Scalded skin syndrome” was a suspected infection obtained from a skin culture from a newborn. Gram-positive, catalase-positive white colonies that were β-hemolytic grew on blood agar. What is the most likely identification?

A. Streptococcus pyogenes
B. Staphylococcus aureus
C. Enterococcus faecalis
D. Streptococcus agalactiae

A

B. Staphylococcus aureus

Harr Micro (12 decks)

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