Medical Microbiology

Medical Microbiology

Medical microbiology is a branch of science that deals with the study of of pathogenic micro-organisms and is concern with disease, diagnosis ,prevention, control and treatment.

Diseases caused by micro-organisms

  • Staphylococcus aureus
    Staphylococcus aureus
    Staphylococcus aureus


1. Morophology

  • Staphylococcus aureus are gram-positive spherical cocci approximately 1 micrometer in diameter.These cells may be arranged in singly,in pairs,shorts chains or in clusters.
  • They are non-spore forming, non-motile.They may be capsulated or non-capsulated.
  • Under influence of some chemicals the cocci form may change into L-forms.

2. Cultural characters

Staphylococcus aureus  colonies on blood agar showing zone of heamolysis.
Staphylococcus aureus colonies on blood agar showing zone of heamolysis.
  • Staphylococcus aureus may readily grow in ordinary media.It can grow on Nutrient agar, MacConkey’s agar.
  • It grow on temperature range of 10° C  to 42° C and optimum temperature for its growth is 37° C
  • Optimum pH is 7.3-7.6.
  • They may be aerobic or facultative anaerobic in nature.
  • The colonies are 2-4 mm in diameter,circular in shapes ,convex and shiny .
  • These organisms are golden yellow pigment producing organism.These pigment production occurs in aerobic cultures at optimum pH at 22°C.
  • Most of the strains of Staphylococcus  aureus show heamolytic activity on blood agar.
  • The Staphylococcus aureus show pink coloured colony due to lactose fermentation on MacConkey’s agar.

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