Laboratory diagnosis and Tests are Staphylococcus

Laboratory diagnosis and Tests are Staphylococcus

Laboratory diagnosis of Staphylococcus:

 1.Specimens: surface swab ,pus ,sputum, Blood ,tracheal aspirate,CSF etc.

 2.Staining : stained smear of specimen reveals gram –positive cocci in grame like clusters.

 3.Culture:

(i)Blood agar: Golden –yellow colored colony →S.aureus & some are β-haemolytic.

(ii)Nutrient agar: Golden –yellow colored colony→ S.aureus.

(iii)7.5% NaCI agar : A  medium containing 7.5% NaCI  is selected medium for S.aureus.

Biochemical tests of Staphylococcus:

Test	S.aureus	S.epidermidis&S.saprophyticus
Catalase test	+ve	+ve
Coagulase test	+ve	-ve
Manitol Fermentation test	+ve	-ve
DNase test	+ve	-ve
Antibiogram test

Coagulates test: 

When the tested organism bringing into contact with plasma, convert fibrinogen to fibrin, it indicates that the organism is coagulates producer.

Requirements:

 1.Slide.

 2.Spreader.

 3.Human plasma.

 4.Distilled water.

Procedure:

 1.Place a drop of distilled water on each side of a slide.

 2.Emulsify a colony of the test organism in each of the drop to make two thick suspensions.

 3.Add a drop of plasma to one of the suspension and mix well.

 4.Look for clumping of the organism within 10 seconds.

 5.On the other suspension ,on need to add plasma and it is used as control.

Result:

 1.Clumping within 10 seconds –pathogen present.

 2.No clumping within 10 seconds –No pathogen.