Cultural Characteristics of Staphylococcus Aureus

Staphylococci grow in a carbon dioxide enriched atmosphere and also well grow aerobically. Most of the strains grows anaerobically, but less well. The Temperature range of S.Cocci is 10–42 ºC, whereas optimum temperature is 35–37 ºC. Colonies on solid media are smooth, glistening, round and raised.

1- Blood Agar & Choclate (Heated Blood) Agar

Staphylococcus Aureus produces occasionally white 1-2 mm in diameter colonies or yellow to cream after overnight incubation. Pigment is less clear in young colonies. Some strains are beta haemolytic in the presence of oxygen. Colonies are easily emulsified and slightly raised.

2- Mannitol Salt Agar

Mannitol Salt Agar is a useful selective medium for S.Aureus. This agar also be used for screen the nasal carriers. S. Aureus ferments the mannitol and is able to grow on agar contaning 70 – 100 g/l sodium cholride. Mannitol Salt agar also be used for isolating Methicillin Resistant Staph Aureus (MRSA) which contain 75g/l sodium cholorid and 4mg/l methicillin.

3- Tryptic Soy Agar

Tryptic Soy Agar is a growth media for different bacteria. It is a non-selective media which provide enough nutrients to allow a wide variety of microorganisms. Staphylococcus show convex and circular colonies on this agar.

4- Biochemical Test

Staphylococcus Aureus is:

• • • • Catalase positive
      • Oxidase negative
      • Coagulase positive
      • Methyl red positive
      • Nitrate reduction positive
      • Beta hemolysis on Blood agar
      • Citrate positive
      • Motility negative
      • Urease positive