LABORATORY DIAGNOSIS

Staphylococci

gram positive cocci, usually in grape like clusters

tetrads

Micrococci typically appear as gram (+) cocci in ___________

Vogel Johnson media

Isolation media for s. aureus only

Sheep’s Blood Agar

Isolation Media 5% SBA

Mannitol Salt Agar

Isolation Media: MSA

Colistin Nalidixic Acid Agar

Isolation Media: CNA

Phenyl Ethyl Alcohol Agar

Isolation Media: PEA agar

Micrococci

Small to medium, opaque colony with gamma hemolysis

Staphylococcus aureus

Medium to large; pigmented creamy yellow “butyrous” colony appearance with beta hemolysis

staphyloxanthin

Staphylococcus aureus has yellow colonies due to ___________

Staphylococcus epidermidis

Small to medium, gray- white colonies with gamma hemolysis

Staphylococcus saprophyticus

Larger colonies, white with gamma hemolysis

Staphylococcus lugdunensis

Medium sized colonies with narrow beta hemolysis

CATALASE TEST

TEST to differentiate genus Staphylococcus and Micrococcus from Streptococcus

3% hydrogen peroxide

Catalase test use _______ reagent

false positive

Use of colonies coming from BAP for catalase test can cause _______

COAGULASE TEST

definitive test for S. aureus it differentiates it from other staphylococci

SLIDE COAGULASE

To detect bound coagulase or clumpy factor

TUBE COAGULASE

To detect free coagulase and clot formation

37

TUBE COAGULASE Will require incubation at ___ degC for 4hrs and if (-) further incubation at RT for 16 hrs

EDTA

MEDIA/ REAGENT used for coagulase test is rabbit’s Plasma collected using ______

false positive

Use of Citrated Plasma in coagulase test is not preferred because it will cause ________

bubbling

Catalase test positive result is ______

MANNITOL FERMENTATION TEST

May be carried out as ID test for S.aureus

phenol and 7.5

MANNITOL FERMENTATION TEST Uses of MSA with _________ red and ____ % salt

yellow

Positive result in MANNITOL FERMENTATION TEST _______ halo around the colonies

red

negative result in MANNITOL FERMENTATION TEST _______

0.1N

DNase TEST HCl PRECIPITATION reagent DNase Agar and _______ HCl

Clearing

DNase TEST HCl PRECIPITATION result ______ of agar around the colonies

Methyl Green or Toluidine Blue

DNase TEST DYE METHOD reagent DNase with either ________ _________ or ________ ______

gram +

able to tolerate salt tolerance and ferment mannitol

CEPHALOSPORINASE TEST

to detect B. lactamase production

cefinase, nitrocefin

In CEPHALOSPORINASE TEST the media uses _______ disk with impregnated substrate _______

pink-red

CEPHALOSPORINASE TEST result is ______ - ____

s. pyogenes

BACITRACIN DISK TEST is used to identify

resistant

BACITRACIN DISK TEST Staphylococci ____

susceptible

BACITRACIN DISK TEST Micrococci ______

NOVOBIOCIN DISK TEST

differential test for CoNS

5 ug

NOVOBIOCIN DISK TEST reagent Use of ____________ Novobiocin antibiotic disc

yellow

Staphylococcus aureus colony color

positive

Staphylococcus aureus catalase test, coagulase test, mannitol Fermentation, DNase Test

beta

Staphylococcus aureus hemolysis on BAP

Susceptible

Staphylococcus aureus NOVOBIOCIN SUSCEPTIBILITY (5 ug)

White

s. epidermidis and s. saprophyticus colony color

positive

s. epidermidis and s. saprophyticus catalase Test

negative

s. epidermidis and s. saprophyticus coagulase Test, Mannitol Fermentation, DNase Test

gamma

s. epidermidis and s. saprophyticus hemolysis on BAP

susceptible

Staphylococcus epidermidis NOVOBIOCIN SUSCEPTIBILITY (5 ug)

resistant

Staphylococcus. saprophyticus NOVOBIOCIN SUSCEPTIBILITY (5 ug)