Systematic Veterinary Bacteriology and Mycology

CULTURAL CHARACTERISTICS

• They are aerobic and facultatively anaerobic.
• They grow at an optimum temperature of 35-37°C.
• Staphylococcus grows in the presence of 7-10% Sodium chloride. Hence media-containing salts is selective for this organism (eg; Mannitol Salt agar) and it is highly inhibitory to many other bacteria particularly Gram-negative bacteria. (Click here for visual)

• In Nutrient agar plate the colonies are round, smooth, glistening, opaque, low, convex, edge, entire end of a golden yellow or white colour.
• In nutrient broth an uniform turbidity is present with powdery sediment.
• Phenolpthaline diphosphate or tellurite agar selectively inhibits non-pathogenic strains.
• Haemolysis on blood agar. Capable of liberating ‘V’ factor into the medium, which favours the growth of Haemophilus organism.
• Purple agar, containing bromocresol purple as a pH indicator and 1% maltose, is used to differentiate S. aureus and S. intermedius.
• Most strains form pigments, hence previously classified as per the colour of the pigment produced.
  • S. aureus – yellowish or golden orange pigment.
  • S. albus - white colonies.
  • S. citreus - lemon yellow colour pigment
• Later on it was found that pigment formation was variable. Hence such classification was no longer followed.
• In sheep or rabbit blood agar plate “double haemolysis” around colonies are formed with incubation at 37°C it produces an incomplete haemolysis, which develops into a complete haemolysis when held at 4°C. This is called as hot cold lysis phenomenon.