LABORATORY DIAGNOSIS: Staphylococcus aureus Flashcards

1
Q

beta – hemolytic pattern
golden yellow

A

BLOOD AGAR

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2
Q

contains 7.5% to 10% sodium chloride

A

MANNITOL SALT AGAR

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3
Q

inhibits gram – negative organism

A

PHENYL ETHYL ALCOHOL (PEA)
COLISTIN NALIDIX ACID AGAR (CNA)

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4
Q

Selective and differential for
isolation of MRSA (+) mauve/pink
colored colonies

A

CHROM agar

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5
Q

Coagulase is an enzyme that converts soluble fibrinogen into soluble fibrin

A

Coagulase Tests

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6
Q

is the only significant human pathogen that possessess the coagulase enzyme

A

Staphylococcus aureus

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7
Q

Principle:
Fibrinogen _______________Fibrin
(+) white fibrin clots
(-) Smooth suspension

A

Coagulase test

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8
Q

Cell bound coagualse

A

Slide

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9
Q

Free coagulase

A

Tube –

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10
Q

Uses ___ (anticoagulated with EDTA) for coagulase test

A

Rabbit plasma

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11
Q

Purpose:
Staphylococcus aureus contains a heat-stable thermonuclease and coagulase negative staphylococcus does not.

A

THERMONUCLEASE TEST

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12
Q

A rapid test to differentiate between the two organisms. : heat-stable thermonuclease and coagulase negative

A

THERMONUCLEASE TEST

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13
Q

THERMONUCLEASE TEST: Positive:

A

Pink zone of clearing at the edge of the well with a darker blue ring at the outer periphery of the zone;

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14
Q

use MSA plate; (+) = yellow colored S.
aureus colonies (w/ yellow halo)

A

Mannitol Fermentation test

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15
Q

(+) = jet black colonies

A

Tellurite glycine agar

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16
Q

(+) = pink color acetoin (acetylmethyl carbinol)

A

Voges-Proskauer test

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17
Q

(+) = clear/colorless zone around the test
organism

A

DNase test (DNA-Methyl green agar)

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18
Q

used in detecting both clumping factor and Protein A

A

Latex agglutination test

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19
Q

useful in detecting altered PBP and oxacillin resistant strains

A

Latex agglutination test

20
Q

used for identification of mecA gene

A

Molecular test (Nucleic acid probes or PCR
amplification)

21
Q

gold standard for MRSA detection

A

Molecular test (Nucleic acid probes or PCR
amplification)

22
Q

Drug of Choice for Staphylococcus aureus

A

Penicillin (Drug of Choice)

23
Q

resistant penicillin (Nafcillin, oxacillin,
methicillin)

A

Penicillinase

24
Q

used when isolates are resistant to
the penicillin derivatives

A

Vancomycin

25
Q
  • screened using 6ug/ml VA that is incorporated to BHI agar, (+) = any growth of the medium
A

Vancomycin agar screen plate

26
Q

used to screen MRSA clinical sample
- (+) growth of more than 1 colony
- (-) absence of growth on the agar plate
* resistant to oxacillin → Beta-lactam drugs report as resistant

A

Oxacillin screen plate (MHA w/ 4%NaCl and 6ug/ml oxacillin)

27
Q
  • preferred method for detecting resistance in both S. aureus and S. lugdunensis.
A

Cefoxitin disc diffusion (30ug)

28
Q
  • detect inducible clindamycin resistance in staphylococci
  • 15ug E and 2ug Cd (15-26 mm apart on MHA or BAP)
  • (+) = flattening on one side (near erythromycin disc) of
    the clindamycin ZOI, which gives appearance of a
    “D-zone”
  • (-) absence of blunting indicates E resistance
A

Double-disc diffusion test (D –test)

29
Q

represents 50% - 80% of all coagulase – negative staphylococci

A

Staphylococcus epidermidis

30
Q

organisms that have traditionally been considered skin contaminants, and their recovery from cultures doesn’t always indicate presence of disease.

A

Staphylococcus epidermidis

31
Q

account for a large number of nosocomial and opportunistic pathogen in immunocompromised patient

A

Staphylococcus epidermidis

32
Q

Habitat: Skin & Mucus membrane

A

Staphylococcus epidermidis

33
Q

Mode of Transmission: sterile site by implantation of medical devices e.g. shunts, prosthethic devices; human serves as exogenous or endogenous source
of infection

A

Staphylococcus epidermidis

34
Q

Bacteremia associated with the use of catheter, orthopedic/prosthetic
implants, CNS shunt, pacemaker

A

Staphylococcus epidermidis

35
Q

Stitch abscess, endocarditis, UTIs,

A

Staphylococcus epidermidis

36
Q

Habitat: human skin, peri – urethral and urethral area

A

Staphylococcus saprophyticus

37
Q

second most common pathogen associated with UTIs causing 10-20% of all UTIs in sexually active young women

A

Staphylococcus saprophyticus

38
Q

The virulence factors of S. saprophyticus include

A

adherence to urothelial cells by means of a surface- associated protein, lipoteichoic acid; a hemagglutinin that binds to fibronectin, a hemolysin; and production
of extracellular slime.

39
Q

It infects humans through sexual intercourse or through contact with animals.

A

Staphylococcus saprophyticus

40
Q

Urinary tract infection in young sexually active adolescent female (Cystitis)

A

staphylococcus saprophyticus

41
Q

Urinary tract infection in young sexually active adolescent female (Cystitis)

A
42
Q

burning sensation when passing urine,
the urge to urinate more often than usual, a dripping effect’ after urination, weak bladder, a bloated feeling with sharp razor pains in the lower abdomen around the bladder and ovary areas, and razor-like pains during sexual intercourse.

A

staphylococcus saprophyticus

43
Q

Staphylococcus saprophyticus
TREATMENT

A

Ciprofloxacin
Trimethoprim – Sulfamethoxazole
Quinolones such as norfloxacin

44
Q

Catalase positive (+); coagulase negative
(-), non – mannitol fermenter

A

Staphylococcus saprophyticus

45
Q

Novobiocin and Nalidixic acid
resistant

A

Staphylococcus saprophyticus

46
Q

novobiocin sensitive

A

Staphylococcus epidermidis