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I.BETA-HAEMOLYTIC STREPTOCOCCI
In general,
these produce soluble haemolysin that can be recognized readily on
culture. They elaborate specific carbohydrate antigens (C.
antigen). These antigens give reaction with specific antisera that
permit arrangement into groups (Lancefield group antigens A-H and K-V).
STREPTOCOCCUS PYOGENES
Click here to read more.(LANCEFIELD GROUP A)
STREPTOCOCCUS AGALACTIAE
(GROUP B)
Is a member of the
normal flora of the female genital tract and an important cause of
neonatal sepsis and meningitis. Infections such as pneumonia,
endocarditis, meningitis, cellulitis, arthritis can also occur in
adults, particularly in the immunocompromised host. In animals, it is a
common cause of mastitis in cattle.
GROUP C AND G
Occur somtimes in
the pharynx, may cause sinusitis, bacteraemia or endocarditis.
STREPTOCOCCUS FEACALIS
(GROUP D)
Group D includes
entercocci (e.g. Enterococcus faecalis). Enterococcus faecalis is
constantly present as a commensal in the intestine and therfore in the
faeces; it is sometimes present in the oral flora.
It may cause urinary tract infections, endocarditis, biliary tract infections, suppurative abdominal lesions and ear infections in man. 
Morphology :
Gram positive cocci in pairs or in short chains, non motile and non-capsulated.  
Culture :
Grows readily on ordinary culture media and on MacConkey's agar minute lactose fermenting colonies, on blood agar the colonies form zones of β-haemolysis, sometimes α-haemolysis and sometimes the colonies are non-haemolytic. Enterococci also grow on media with a high salt content 6.5% NaCl. Enterococcus faecalis grows within a wide temperature range 10-45°C. 
Biochemical Reaction :
Ferments mannitol with gas production.
Resistance :
Withstand heat at 60°C for 30 minutes (heat resistance test), a distinguishing feature from other streptococci. Inhibited but not killed by penicillin.
GROUPS E, F, H AND K-V
Occur primarily in
animals.
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I.BETA-HAEMOLYTIC STREPTOCOCCI
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