LABORATORY DIAGNOSIS: Staphylococcus aureus Flashcards
beta – hemolytic pattern
golden yellow
BLOOD AGAR
contains 7.5% to 10% sodium chloride
MANNITOL SALT AGAR
inhibits gram – negative organism
PHENYL ETHYL ALCOHOL (PEA)
COLISTIN NALIDIX ACID AGAR (CNA)
Selective and differential for
isolation of MRSA (+) mauve/pink
colored colonies
CHROM agar
Coagulase is an enzyme that converts soluble fibrinogen into soluble fibrin
Coagulase Tests
is the only significant human pathogen that possessess the coagulase enzyme
Staphylococcus aureus
Principle:
Fibrinogen _______________Fibrin
(+) white fibrin clots
(-) Smooth suspension
Coagulase test
Cell bound coagualse
Slide
Free coagulase
Tube –
Uses ___ (anticoagulated with EDTA) for coagulase test
Rabbit plasma
Purpose:
Staphylococcus aureus contains a heat-stable thermonuclease and coagulase negative staphylococcus does not.
THERMONUCLEASE TEST
A rapid test to differentiate between the two organisms. : heat-stable thermonuclease and coagulase negative
THERMONUCLEASE TEST
THERMONUCLEASE TEST: Positive:
Pink zone of clearing at the edge of the well with a darker blue ring at the outer periphery of the zone;
use MSA plate; (+) = yellow colored S.
aureus colonies (w/ yellow halo)
Mannitol Fermentation test
(+) = jet black colonies
Tellurite glycine agar
(+) = pink color acetoin (acetylmethyl carbinol)
Voges-Proskauer test
(+) = clear/colorless zone around the test
organism
DNase test (DNA-Methyl green agar)
used in detecting both clumping factor and Protein A
Latex agglutination test