MORPHOLOGY OF STAPHYLOCOCCUS AUREUS
- Shape – Round shape (cocci)
- Size – 1 micron (diameter)
- Arrangement of cells – Grape-like clusters
- Motility – Non-motile
- Flagella – Non-flagellated
- Spores – Non-sporing
- Capsule – present in some strains
- Gram Staining reaction – Gram +ve
CULTURE REQUIREMENTS OF STAPHYLOCOCCUS AUREUS
⇒ Special requirements – No special requirements for culture, readily grows on Ordinary culture media.
⇒ Optimum temperature – 10-42°C
⇒ Optimum pH – 7.4-7.6
⇒ Salt requirements – No special requirements but can tolerate 8-10% salt concentration, useful in culturing Staph aureus in the mixture of bacteria. Many human pathogens cannot tolerate high salt concentrations, adding salt to high concentration makes the selective media for staph aureus.
⇒ Oxygen requirements – Staph aureus is Aerobe and Facultative anaerobe.
⇒ Various culture media for Staphylococcus aureus –
- Nutrient Agar medium
- Blood Agar medium
- MacConkey Agar medium
- Mannitol Salt Agar medium
- Milk agar
- Liquid medium
⇒ Selective media for Staphylococcus can be prepared by incorporating 8-10% NaCl, LiCl, Tellurite or Polymixin in the NAM or other media makes them selective for the growth of Staph aureus.
CULTURAL CHARACTERISTICS OF STAPHYLOCOCCUS AUREUS
Cultural Characteristics NAM (Nutrient Agar Medium MacConkey agar medium Blood Agar Medium Mannitol Salt Agar Milk Agar
Shape Circular Circular Circular Circular Circular
Size 2-4 mm 2-4 mm 1-4 mm 2-4 mm 3-5 mm
Elevation Convex Convex Convex Convex Convex
Surface Smooth Smooth Smooth Smooth Smooth
Color Golden yellow Pink Light golden yellow, surrounded by clear zone (beta hemolysis). Yellow Golden yellow (Pigment production enhanced).
Structure Opaque Opaque Opaque Opaque Opaque
Emulsifiability Easily emulsifiable Easily emulsifiable Easily emulsifiable Easily emulsifiable Easily emulsifiable
In liquid culture media like peptone water and Nutrient broth, uniform turbidity is produced which is further analyzed for the morphology (under the microscope), gram reaction, biochemical tests, and staphylococcus specific tests.
That’s all about the Morphology & Cultural Characteristics of Staphylococcus aureus
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