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Clinical Micro Final Exam > Gram Pos, Catalase Neg, Aerobic Cocci > Flashcards

Gram Pos, Catalase Neg, Aerobic Cocci Flashcards

1
Q

Lower respiratory tract: normal flora?

A

No. Typically sterile

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2
Q

Streptococci spp. are _____ ______

A

facultative anaerobes

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3
Q

Streptococci spp cat? oxidase?

A

Catalase -

Oxidase -

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4
Q

Which two may require increased CO2 for growth?

A

S. Pneumoniae and viridans strep

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5
Q

Susceptibility testing is needed for:

A

Strep pneumoniae and viridans strep

*as a result of antibiotic resistance to PENICILLIN and CEPHALOSPORINS.

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6
Q

Susceptibility testing is not needed for:

A

Strep pyogenes, Strep agalactiae, Groups C, F, and G

  • Penicillin is drug of choice*
    • If allergic, erythromycin is drug of choice but requires susceptibility testing as resistance has been discovered.*
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7
Q

Which organisms are considered normal flora?

A

Strep agalactiae (female genitourinary tract, lower GI)
Lancefield groups C,F, and G (skin, nasopharynx, GI, GU)
Strep pneumoniae (nasopharynx)
Viridans strep (oral cavity, GI, female genital)
Enterococcus (E.faecalis and E. faecium- GI and female GU)

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8
Q

Which organism is not normal flora?

A

Strep pyogenes

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9
Q

What hemolysis is displayed by Viridans strep?

A

Alpha hemolysis (green color)

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10
Q

What hemolysis is displayed by Enterococcus spp?

A

Gamma hemolysis

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11
Q

Which of the Lancefield groups are clinically significant?

A

Groups A,B,C,D,F, and G

Group A contains group A antigen…..

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12
Q

Who is in group A and hemolysis

A

Strep pyogenes-beta hemolysis

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13
Q

Who is in group B and hemolysis

A

Strep agalactiae- beta hemolysis

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14
Q

Who is in group C and hemolysis

A

S. equisimilis- most common group C in humans
S. zooepidemicus- animal diseases. Humans can get through unpasteurized milk and cheeses
Beta hemolysis

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15
Q

Who is in group D and hemolysis

A

S. bovis
S. equinus
alpha or gamma hemolysis

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16
Q

What is the hemolysis of Strep pneumoniae?

A

Alpha

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17
Q

Which strep species is the common cause of dental carries?

A

Strep mutans

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18
Q

Which strep group is susceptible to Bacitracin?

A 
Group A (S. pyogenes) 
*Not recommended anymore due to groups C and G also being susceptible.*
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19
Q

Which organism is susceptible to optochin?

A

S. pneumoniae

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20
Q

What does the bile solubility test detect? Which organism is it diagnostic for? How are positive positive tests indicated by?

A

It detects amidaae enzyme. Diagnostic for S. pneumoniae. Positive tests are indicated by cell lysis.

21
Q

Which organisms are PYR +

A

Group A (S. pyogenes) and Enterococcus spp

22
Q

Explain the concept of the PYR test

A

Substrate L-pyrrolidonyl-b-napthlyamide is hydrolyzed by the enzyme pyrrolidonyl arylamidase (PYR) to create beta -napthylamide which changes color when PYR reagent added forming a pink/ red color.

23
Q

What organisms are ID by the hippurate hydrolysis? How does it work?

A

Group B Strep, Gardnerella vaginalis, Campylobacter jejuni, and Listeria monocytogenes
Hydrolyzes sodium hippurate due to presence of enzyme hoppuricase forming a purple color.

24
Q

What organism is differentiated from other strep spp. using the CAMP test?

A

S. agalactiae

25
Q

Which organisms are positive when incubated in bile esculin agar?

A 
Group D (S. bovis and Enterococci)
*Pos= blackening of the media*
26
Q

How does the bile esculin agar work?

A

If pos, organism has the ability to grow in bile and hydrolyze esculin to esculetin which reacts with Fe in the medium forming dark precipitate.

27
Q

What is the salt tolerance test used for?

A

To differentiate Enterococci (pos) from Group D Strep (neg).

Broth starts purple. Positive turns yellow or turbid.

28
Q

How do slide agglutination kits work?

A

Latex beads are coated with group specific anti-serum, which clump when mixed with a small amount of colony from the specific Strep spp.

29
Q

What organism has colonies that are gray-white and surrounded by large zones of beta hemolysis?

A

Strep pyogenes

30
Q

Which organism is a common pathogen in throat swabs?

A

Strep pyogenes

*Throat swabs: inoculate to SBAP with SXT (trimethoprim-sulfamethoxazole) which inhibits growth of normal flora.

31
Q

What are the virulence factors of Strep pyogenes?

A

Streptolysin O- causes lysis of erythrocytes, leukocytes, and platelets. Oxygen liable. Will see clearing in the subsurface adjacent to the stab marks. Antigenic
Streptolysin S- causes lysis of erythrocytes, leukocytes, and platelets. Oxygen stable. Produces hemolysis on BAP. Non-antigenic.
M protein- Induce antibody formation
Streptococcal pyrogenic exotoxins (SPE’s)- Induce fever and inflammation with release of many immune mediators which can induce shock and organ failure.

32
Q

What are some diseases from Strep pyogenes?

A

Necrotizing Fasciitis (flesh eating bacteria)- affects deep subcutaneous tissues; death of muscle, skin, and fat.
Streptococcal Toxic Shock Syndrome induced by SPE’s- Patients are bacterimic and have necrotizing fasciitis.
Acute exudative pharyngitis (strep throat)- complication in children is glomerulonephritis.

33
Q

Which organism is the leading cause of morbidity and mortality in neonates in the US?

A

Strep agalactiae

Exposed during birthing process once membranes rupture.

34
Q

What are pregnant women screened for? What samples are used?

A

Group B strep. If pos, they’ll receive intravenous antibiotics during labor.
Vaginal and rectal swabs (need both)

35
Q

Which organism is alpha hemolytic, small gray colonies with central depression that develops with age (doughnut)?

A

Strep pneumoniae

36
Q

Which organism is the leading cause of bacterial pneumonia and meningitis?

A

Strep pneumoniae

37
Q

Who is most at risk from Strep pneumoniae?

A

Children under 2 and adults over 65

38
Q

What is the vaccine for Strep pneumoniae for children called?

A

PCV 13

39
Q

What is the vaccine for Strep pneumoniae for the elderly or adults with asthma or who smoke called?

A

PPSV23

40
Q

True/ false? Viridans strep are bile esculin pos.

A

False. They’re neg which differentiates from Enterococcus and Group D Strep.

41
Q

Viridans strep possess non group ____

A

Antigens

42
Q

Enterococcus spp. are resistant to:

A

Cephalosporins and aminoglycosides

Becoming increasingly resistant to Vancomycin (VRE’s)

43
Q

Most infections of Enterococcus are:

A

Hospital aquired UTI’s (nosocomial)

44
Q

What is the treatment for Enterococcus spp?

A

Combination of vancomycin and an aminoglycoside.

45
Q

What does the pyruvate broth differentiate?

A

E. faecalis (pos) and E. faecium (neg)

46
Q

Which organism is the only Catalase neg cocci that are vancomycin resistant, PYR and Leucine aminopeptidase test (LAP) neg that produce CO2 from glucose?

A

Leuconostoc spp.

47
Q

What is the natural habitat of Leuconostoc spp?

A

Plants, veggies, and dairy products.
Rarely a pathogen (immunocompromised)
1st considered a contaminant

48
Q

What are all spp of Leuconostoc resistant to?

A

Vancomycin

Clinical Micro Final Exam (4 decks)

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