Staphylococcus
Mainly parasitic , facultative anaerobic cocci , producing acid form glucose under anaerobic condition give +ve catalase and –ve oxidase test .It is sensitive to
lysostaphin .
They are usually found on the skin or mucous membrane of the animal body , especially of the nose and mouth where they often occur in large number even under normal condition .
Staph. aureus :
Distinguished primarily by it's ability to produce coagulase , is notorious as the case of suppurative condition ( pyogenic or pus forming ) , mastitis of women & cow, boil , carbuncles , infantile impetigo , internal abscesses , and food poisoning .
Staph. epidermidis : ( Staph. albus . )
Is a lesser pathogen or commensal on the skin and mucous membranes .
Staph. saprophyticus : ( Staph. citrus )
Non-pathogenic bacteria , a lemon-yellow colored colonies on nutrient agar medium
The properties of Staph. aureus are as follows :
1. Ferment mannitol and lactose .
[]2.[/ Proteolytic .
[3.[/ Produce coagulase ( an enzyme-like principle that cause citrated blood to coagulate ) .
[4.[/] Produce golden pigment .
[5.[/] = lipase .
[6.[/= wide zone of hemolysis aerobically in Blood agar platesze] .
[7.[/ Grow in medium containing 10 % NaCl (staphylococcus 110 ) , this medium is specially designed to select Staph. aureus it contains
[1. Protein digest 1.00 %
[]2. Yeast extract 0.25 %
[3.[/] gelatin 3.00 %
[4.[/] D-manniotol 1.00 %
[5.[/] Lactose 0.20 %
[6.[/] NaCl 7.50 %
[7.[/] K2HPO4 0.50 %
[]8.[/] Agar 1.50 %
[9.[/ Phenol red indicator
Coagulase : It acts only in conjunction with a serum factor called Coagulase Reactive Factor ( CRF ) the normal coagulation of blood as follows :
Prothrombin + prothrombinase + CaCl2 ------------- Thrombin
Fibrinogen------------------------------- Fibrin ( = clot ) .
The role of staphylococcal coagulase appear to be to displace both
Prothrombinase and Prothrombin .
[4]CRF + Coagulase ----------- CRF Coagulase ]
[ CRF-Coagulase[]Fibrinogen--------------------- Fibrin (= clot ]
Demonstration of coagulase : Many method for detecting coagulase have been described . A simple technique is as follows :
0.5 ml. Young broth culture
+ 0.5 ml . Fresh lyophilized citrated plasma ( human )
The plasma must be free from fibrinolytic properties and coagulase inhibitors.
Another method is :
0.1 ml. Overnight broth culture of OM .
+ 0.9 ml. 1\10 diluted rabbit plasma
In a glass tube and is incubated at 37'C for 24 hrs.
Lab. Diagnosis : One or of the following specimens may be collected for ex ;
1. Pus from abscesses , in a screw – capped contained or swab .
2. Sputum from cases of lower respiratory infection saliva from mouth .
3. Faeces or vomit frompatients with food poisoning 1-5 ml. in a universal container .
4. Blood from patients suspected bacteriamia .
5. Urine from patients with cystitis or pyelonephritis .
6. Anterior nasal secretion by swab .
A - The specimen is generally examined as follows :
1. Gm stained smear except in case of blood and swab .
2. Culture on blood , nutrient , or milk agar ---------- Golden cream- colored or white colonies .
3. Coagulase test + ve .
B - Sensitive test .
C - Phage – type or serotype of the isolated strain
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الأربعاء سبتمبر 30, 2009 4:43 am
