Streptococci
Morphology
Streptococci are gram positive cocci which are arranged in chains or pairs. They are part of normal human flora cause pathogenic infection.
Classification of Streptococcus
Based on oxygen
1. Aerobic
Growth on BA (blood agar) medium
a. Alpha haemolysis
Incomplete haemolysis (green colour)
Streptococcus viridans
Streptococcus Pneumonia
b. Beta haemolysis
Complete haemolysis
(Clear)
Lancefield grouping
specific C carbohydrate Ag on cell wall
Group A- U(21 groups)
Group A
Streptococcus pyogenes
Group B
Streptococcus agalactiae
Group C
Streptococcus equisimilis
Group D
(Enterococcus)
Other group
c. Gamma haemolysis
No haemolysis
Enterococcus fecalis
2. Anaerobic
Peptostrreptococci
Characteristics
Small, spherical or oval or circular like colonies appear in incubation at 37 degree Celsius.
Non motile and non sporing
Grows well in enriched medium
Haemolytic reaction (Alpha, beta and gamma) obsoved on blood agar medium.
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