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BACTE MIDTERMS > B1.3 > Flashcards

B1.3 Flashcards

1
Q

Other Staphylococci classifications

A

S. epidermidis
S. saprophyticus
S. lugdunensis
Other Coagulase-Negative Staphylococci
Methicillin-Resistant Staphylococci aureus (MRSA)
Vancomycin-Resistant Staphylococci
Macrolide Resistance

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2
Q

indigenous microbiota of the skin
contaminant of medical instruments, catheters, CSF shunts and prosthetic heart valve implants (implanted medical devices), hip
prostheses

A

Staphylococcus epidermidis

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3
Q

Staphylococcus epidermidis disease caused

A

: Stitch abcess,
Health care-acquired UTIs,
Endocarditis,
Bacteremia

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4
Q

In charge for the adherence of S. epidermidis

A

Poly-γ-DL-Glutamic Acid (PGA)

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5
Q

LABORATORY DIAGNOSIS used for detecting S. epidermidis

A

Blood agar plate
Biochemical Test
Susceptibility with 5-ug NOVOBIOCIN (16mm-27mm)

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6
Q

Blood agar plate result for S. epidermidis

A

gray to white, opaque, small to medium-sized pinheads and non-hemolytic colonies

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7
Q

Biochemical test results for S. epidermidis

A

Coagulase (-),
CNA (+),
DNase(-),
Mannitol Fermentation (-)

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8
Q

present on the normal skin and in the periurethral and urethral flora
adheres effectively to the epithelial cells lining the urogenital tract

A

Staphylococcus saprophyticus

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9
Q

Staphylococcus saprophyticus disease caused

A

common cause of UTI in young sexually active women

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10
Q

significant result for urine culture in order to determine infection by S. saprophyticus

A

urine culture <10,000 CFU/ml

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11
Q

LABORATORY DIAGNOSIS used to determine S. saprophyticus

A

Blood agar plate
Biochemical test
Resistance to NOVONIOCIN (5ug; 6mm-12mm) and NALIDIXIC ACID
Absence of Phosphatase production

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12
Q

Blood agar plate result for S. saprophyticus

A

white, opaque, slightly larger than pin-heads, nonhemolytic colonies although some strains produce yellow pigments

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13
Q

Biochemical Test results for S. saprophyticus

A

Coagulase (-),
Dnase (-)
Mannitol Fermentation (-)

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14
Q

Staphylococcus lugdunensis results in coagulase test

A

clumping factor (+),
tube coagulase (-)

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15
Q

contain mecA gene that encodes oxacillin resistance
more aggressive than other CoNS in inefectivity

A

Staphylococcus lugdunensis

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16
Q

Staphylococcus lugdunensis disease caused

A

infective endocarditis,
septicemia,
meningitis,
skin and soft tissue infections,
UTIs, and
septic shock

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17
Q

Other Coagulase-Negative Staphylococci that causes endocarditis, septicemia, and wound infections

A

S. warneri,
S. capitis,
S. simulans,
S. hominis, and
S. schleiferi

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18
Q

Other Coagulase-Negative Staphylococci that causes wounds, bacteremia, endocarditis, and UTIs

medium-sized colonies, with moderate or weak hemolysis and variable pigment production

A

S. haemolyticus

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19
Q

NOVOBIOCIN SUSCEPTIBLE CoNS

A

S. epidermidis
S. capitis
S. haemolyticus
S. hominis subsp. hominis
S. lugdunensis
S. saccharolyticus
S. warneri

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20
Q

NOVOBIOCIN RESISTANT CoNS

A

S. saprophyticus
S. cohnii
S. kloosii
S. xylosus

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21
Q

RESISTANT GENES PRODUCED BY STAPHYLOCOCCI

A

a. Erythromycin Ribosomal Methylase (ERM) Gene

b. Methionine Sulfoxide Reductase (MSR) A Gene

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22
Q

Class of enzyme inactivating genes
Codes for the methylation of the 23s rRNA
Results in resistance to erythromycin
Inducible or constitutive resistance to clindamycin
May not be detected in routine susceptibility testing
Confer cross-resistance to macrolides (erythromycin) and streptogramins (quinupristin)

A

Erythromycin Ribosomal Methylase (ERM) Gene

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23
Q

Codes for efflux mechanism

A

Methionine Sulfoxide Reductase (MSR) A Gene

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24
Q

resistance to erythromycin but susceptibility to clindamycin

A

efflux mechanism

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25
Q

type of S. aureus that is resistant to methicillin, nafcillin, and oxacillin
 acquired after prolonged stay in the hospital, close contact with carriers, effects of broad spectrum antibiotic treatments and exposure to nasal secretions

A

Methicillin-Resistant Staphylococci aureus (MRSA)

26
Q

treatment of choice for MRSA

A

VANCOMYCIN

27
Q

Methicillin-Resistant Staphylococciaureus (MRSA) types

A

Community-Associated MRSA (CA-MRSA),

Health Care–Associated Community-Onset (HACOMRSA),

Hospital-Associated (HA-MRSA)

28
Q

codes for altered Penicillin-Binding
Protein (PBP) = PBP2a or PBP2′

A

mecA

29
Q

LABORATORY DIAGNOSIS for identifying MRSA

A

a. OXACILLIN-SALT AGAR PLATE
b. CHROMOGENIC TEST
c. Latex Agglutination
d. Molecular Nucleic Acid Probes or PCR
Amplification

30
Q

used to screen for MRSA in clinical samples
differentiate MRSA from hyperproducers of β-lactamase, or Borderline Oxacillin-Resistant Staphylococcus aureus (BORSA)

A

OXACILLIN-SALT AGAR PLATE

31
Q

Chromogenic Selective Differential Media:

A

MRSA Select,
Spectra MRSA,
CHROMagar MRSA

32
Q

Substance used in chromogenic test that inhibits non-MRSA

A

CEFOXITIN

33
Q

Results from CHROMOGENIC test for MRSA

A

Changes in color of MRSA colonies within 24 to 48 hours using CHROM Agar against colonies of non-MRSA

34
Q

CHROM agar MRSA colonies color

A

Mauve-colored colonies

35
Q

detect altered PBPs
alternative method for testing and confirmation of oxacillin resistance
 performed on both CoNS and S. aureus

A

Latex Agglutination

36
Q

“gold standard” for MRSA detection

A

Molecular Nucleic Acid Probes or PCR
Amplification

37
Q

Vancomycin-Resistant Staphylococci screening used

A

Vancomycin Agar Plate

38
Q

discrepant macrolide test results (erythromycin resistant and clindamycin susceptible)

A

MODIFIED DOUBLE DISK DIFFUSION TEST (D-zone test)

39
Q

BETA-LACTAMASE TESTS types

A

Cephalosporinase Test
Acidimetric Method
Iodometric Method

40
Q

uses cephalosporin or cefinase disk
 Substrate: nitrocefin

A

Cephalosporinase Test

41
Q

Cephalosporinase Test result for Staphylococci

A

 (+) result: deep pink or red color within 10 minutes (60 minutes for Staphylococci)

42
Q

Acidimetric Method

 Reagent:
 pH indicator:
 (+) result:

A

 Reagent: citrate-buffered penicillin
 pH indicator: phenol red
 (+) result: red  yellow (penicilloic acid = decrease pH)

43
Q

Iodometric Method
 Reagent:
 (+) result:
 (-) result:

A

 Reagent: citrate-buffered penicillin and starch iodine complex

 (+) result: colorless solution- penicilloic acid reduces iodine and prevents it to combine with starch

 (-) result: purple (no color change)8

44
Q

ANTIMICROBIAL TESTING Treatment

A

methicillin,
oxacillin,
nafcillin,
cloxacillin, and
dicloxacillin (penicillinase-resistant penicllin drugs)

45
Q

most commonly used treatment for Antimicrobial testing

A

Oxacillin

46
Q

Cutaneous infections treatment used

A

oral oxaillin or dicloxacillin, if allergic, erythromycin may be substituted

47
Q

Systemic infections treatment used

A

parenteral nafcilllin or oxacillin, if allergic,
vancomycin or cephalosporin may be used

48
Q

MRSA treatment used

A

vancomcin alone or in a combination with rifampicin

49
Q

ANTIMICROBIAL TESTING types

A

A. Screening Test for MRSA: Oxacillin Screen Plate

B. Cefoxitin Disk Diffusion (30 ug)

C. Macro E Test

D. Vancomycin Agar Screen Plate

50
Q

A. Screening Test for MRSA: Oxacillin Screen Plate culture media used

A

MHA with 4% NaCl and 6 ug/mL oxacillin

51
Q

Screening Test for MRSA: Oxacillin Screen Plate procedure

A

spot inoculated with cotton swab and incubated for 24 hours at 35°C

52
Q

Microdilution Testing procedure for MRSA screening

A

oxacilin in cation-supplemented MH broth containing 2% NaCl

53
Q

Result for Oxacillin Screen Plate for MRSA

A

Resistant- growth of more than one colony
Susceptible- no growth on the agar plate

54
Q

Result for Oxacillin Screen Plate for CoNS

A

 Resistant- 24 mm zone of inhibition
 Susceptible- >25 mm zone of inhibition

55
Q

Disadvantage of Oxacillin Screen Plate

A

Does not reliably detect oxacillin-resistant
CoNS

56
Q

preferred method for detection of oxacillin-resistance for both S. aureus and S. lugdunensis

Improves detection of MRSA
serves to induce greater PBP2a in mecA-containing strains

Test reagent to detect resistance- both MIC and diffusion method

A

Cefoxitin Disk Diffusion (30 ug)

57
Q

Cefoxitin Disk Diffusion (30 ug) interpretation

A

Resistant- < 21 mm
Susceptible- > 22 mm

58
Q

detection of heteroresistant VISA because the test uses a higher concentration of organisms (1 x 108 bacteria/ mL)

A

Macro E Test

59
Q

best method for detection of either Vancomycin-resistant S. aureus (VRSA) or VISA

A

Vancomycin Agar Screen Plate

60
Q

Vancomycin Agar Screen Plate

S. aureus should be screened with

A

6-ug/mL vancomycin incorporated into BHIA

61
Q

Confirmatory test for oxacillin resistance

A

Broth dilution and E-test

BACTE MIDTERMS (17 decks)

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