8.5 Gram-Positive and Gram-Negative Cocci Flashcards
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
B. Catalase
** 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 the options
A. Fermentation of glucose (OF tube)
Lysostaphin is used to differentiate Staphylococcus from which other gram-positive, catalase-positive organisms?
A. Streptococcus
B. Aerococcus
C. Micrococcus
D. Enterococcus
C. Micrococcus
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 the options
D. All of the options
Which of the following enzymes contribute to the virulence of S.aureus?
A. Urease and lecithinase
B. Hyaluronidase and Beta-lactamase
C. Lecithinase and catalase
D. Cytochrome oxidase
B. Hyaluronidase and Beta-lactamase
Toxic shock syndrome is attributed to infection with:
A. Staphylococcus epidermidis
B. Staphylococcus hominis
C. Staphylococcus aureus
D. Staphylococcus saprophyticus
C. Staphylococcus aureus
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. Staphylococcus intermedius
** 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
D. All of the above
Slime production is associated with which Staphylococcus species?
A. Staphylococcus aureus
B. Staphylococcus epidermidis
C. Staphylococcus intermedius
D. Staphylococcus saprophyticus
B. Staphylococcus epidermidis
Strains of Staphylococcus species resistant to the Beta-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. Heteroresistant
** S. saprophyticus is best differentiated from S. epidermidis by its resistance to:**
A. 5 ug of lysis taps in
B. 5 ug of novobiocin
C. 10 units of penicillin
D. 0.04 unit of bacitracin
B. 5 ug of novobiocin
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 = Beta
Mannitol salt plate = + (acid production)
What is the most probable identification?
A. Staphylococcus saprophyticus
B. Staphylococcus epidermidis
C. Staphylococcus aureus
D. Staphylococcus hominis
C. Staphylococcus aureus
S. aureus can produce fibrinolysins that dissolve the clot formed by the coagulase enzyme. The tube method calls for an incubation of 4 hours at 35 C to 37 C and 18 to 24 hours at room temperature. Both must be negative to interpret the result as coagulase negative. This organism is coagulase positive and, therefore, identified as S. aureus.
** 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
Ampicillin = S
Cephalothin = R
Cefoxitin = R
Vancomycin = S
Methicillin = R
Which is the drug of choice for treating this infection?
A. Penicillin
B. Ampicillin
C. Cephalothin
D. Vancomycin
D. Vancomycin
**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. Acetoin
** A gram-positive coccus recovered from a wound ulcer from a 31-year-old patient with diabetes showed pale yellow, creamy, Beta-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.
C. Micrococcus spp.
**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
D. Novobiocin susceptibility
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. Beta-Hemolysis on blood agar
C. Mannitol salt agar plate
D. All of these options
D. All of these options
Furazolidone (Furoxone) susceptibility is a test used to differentiate:
A. Staphylococcus spp. from Micrococcus spp.
B. Streptococcus spp. from Staphylococcus spp.
C. Straphylococcus spp. from Pseudomonas spp.
D. Streptococcus spp. from Micrococcus spp.
A. Staphylococcus spp. from Micrococcus spp.
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. Micrococcus spp. from Staphylococcus spp.
Which of the following tests will rapidly differentiate micrococci from staphylococci?
A. Catalase
B. Coagulase
C. Modified oxidase
D. Novobiocin susceptibility
C. Modified oxidase
** 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, Beta-hemolytic, catalase positive
D. May be alpha-, beta-, or y-hemolytic, catalase positive
B. Facultative anaerobic, oxidase negative, catalase negative
Which group of Beta-hemolytic streptococci is associated with erythrogenic toxin production?
A. Group A
B. Group B
C. Group C
D. Group G
A. Group A
A fourfold rise in titer of which antibody is the best indicator of a recent infection with group A Beta-hemolytic streptococci?
A. Anti-streptolysin O
B. Anti-streptolysin S
C. Anti-A
D. Anti-B
A. Anti-streptolysin O
The L-pyrrolidonyl-Beta-napthylamide (PYR), hippurate, and CAMP tests can be used for the presumptive identification of which group of Beta-hemolytic streptococci?
A. Group A and B
B. Group C and D
C. Group C
D. Group F
A. Group A and B
To diagnose streptococcal pharyngitis, primary plates of blood agar and blood agar with sulfamethoxazole-trimethoprim (SXT) are used to differentiate which streptococci?
A. alpha-Hemolytic streptococci
B. Beta-Hemolytic streptococci
C. Streptococcus pneumoniae
D. Enterococcus faecalis
B. Beta-Hemolytic streptococci
Beta-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
D. Bacitracin: Susceptible or resistant, Sulfamethoxazole-Trimethoprim: Susceptible
** 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. Candle jar or CO2 incubator
Which test is used to differentiate alpha-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
D. Bile esculin test
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
B. Streptococcus pneumoniae colonies on a blood agar plate
** S.pneumoniae* and the alpha-hemolytic viridans streptococci can be differentiated by which test?**
A. Optochin P disk test, 5 ug/mL or less
B. Bacitracin A disk test, 0.04 unit
C. CAMP test
D. Bile esculin test
A. Optochin P disk test, 5 ug/mL or less
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
D. Enterococcus faecalis
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
B. Group B streptococci
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
D. *Streptococcus pneumoniae
The PYR hydrolysis test is a presumptive test for which group of Beta-hemolytic streptococci?
A. Group A and Enterococcus
B. Group A and B *Beta-hemolytic streptococci
C. Non-group A or non-group B Beta-hemolytic streptococci
D. Streptococcus pneumoniae and Streptococcus bovis
A. Group A and Enterococcus
A pure culture of Beta-hemolytic streptococci recovered from a leg wound ulcer gave the following reactions:
CAMP test = Neg
Hippurate hydrolysis = Neg
Bile esculin = Neg
6.5% salt = Neg
PYR = Neg
Bacitracin = Resistant
Optochin= 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 streptococci
D. Non-group A, non-group streptococci
Beta-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
Hippurate hydrolysis = +/-
Bile solubility = Neg
6.5% salt = +
PYR = +
Bile esculin = +
SXT = Resistant
Bacitracin = Resistant
Optochin = Resistant
Vancomycin = Resistant
A. Group A streptococci
B. Group B streptococci
C. Enterococcus faecalis, Enterococcus faecium
D. Non-group A, non-group B streptococci
C. Enterococcus faecalis, Enterococcus faecium
** Abiotrophia spp. or nutritionally variant streptococci (NVS) require specific thiol compounds, cysteine, or the active form (pyridoxal) or 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
D. Staphylococcal cross-streak test
Many Beta-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 = +
Bile solubility = Neg
SXT = Resistant
A. Enterococcus faecalis
B. Streptococcus pneumoniae
C. Streptococcus bovis
D. Group B streptococci
A. Enterococcus faecalis
Which two tests best differentiate alpha-hemolytic S. bovis from Streptococcus salivarius which is also alpha-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
B. Starch hydrolysis and acid production from mannitol
Two blood cultures obtained from a newborn grew Beta-hemolytic streptococci with the following reactions:
CAMP test = +
Hippurate hydrolysis = +
Bile solubility = Neg
6.5% salt = +
Bacitracin = Resistant
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
B. Group B streptococci
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. Neisseria gonorrhoeae
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
D. All of these options
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 the options
D. All of the options
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. Neisseria gonorrhoeae
Nonpathogenic Moraxella spp. capable of growing on selective media for Neisseria can 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
B. 10-unit penicillin disk on blood agar
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. Neisseria gonorrhoeae
** The Beta-galactosidase test aids in the identification of which Neisseria species?**
A. Neisseria lactamica
B. Neisseria meningitidis
C. Neisseria gonorrhoeae
D. Neisseria flavescens
A. Neisseria lactamica
Cystine tryptic digest (CTA) media used for identification of Neisseria spp. should be inoculated and cultured in:
A. A CO2 incubator at 35C for 24 hours
B. A CO2 incubator at 42C for up to 72 hours
C. A non-CO2 incubator at 35C for up to 72 hours
D. An anaerobic incubator at 35C for up to 72 hours
C. A non-CO2 incubator at 35C for up to 72 hours
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
D. Neisseria lactamica
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 = +
Oxidase = +
DNase = +
Tributyrin hydrolysis = +
Glucose = Neg
Sucrose = Neg
Lactose = Neg
Maltose = Neg
Fructose = Neg
A. Moraxella catarrhalis
B. Neisseria flavescens
C. Neisseria sicca
D. Neisseria elongata
A. Moraxella catarrhalis
Showing resistance to which drug categorizes a strain of S. aureus as MRSA?
A. Oxacillin
B. Colistin
C. Sulfamethoxazole-Trimethoprim
D. Tetracycline
A. Oxacillin
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 ug oxacillin disk, what is the recommended inhibition zone size for penicillin susceptibility?
A. 5mm or greater
B. 10 mm or greater
C. 15 mm or greater
D. 20 mm or greater
D. 20 mm or greater
Which one of the following organisms is a known producer of B-lactamase-producing strains, and should be tested (screened) by a commerical B-lactamase assay prior to susceptibility testing?
A. Steptococcus pneumoniae
B. Group B streptococci
C. Enterococcus spp.
D. Planococcus spp.
C. Enterococcus spp.
A test for Beta-lactamase production should be performed on all isolates of Staphylococcus and Enterococcus as well as N. gonorrhoeae and H. influenzae. Some organisms may appear to be penicillin/ ampicillin susceptible by the conventional Kirby-Bauer disk diffusion method for Beta-lactamase producers, but still produce small amounts of Beta-lactamase. An example is heteroresistant mecA….
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
B. D-zone test
**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 16 ug/mL or greater
B. MIC of 8 to 16 ug/mL
C. MIC of 4 to 8 ug/mL
D. MIC 8 ug/mL or greater
A. MIC 16 ug/mL or greater
**”Scalded skin syndrome” was a suspected infection obtained from a skin culture from a newborn. Gram-positive, catalase-positive white colonies that were B-hemolytic grew on blood agar. What is the most likely identification?
A. Streptococcus pyogenes
B. Staphylococcus aureus
C. Enterococcus faecalis
D. Streptococcus agalactiae
B. Staphylococcus aureus
