AGf~ICULTURAL RESEARCH, PUSA.

256 PRACTICAL BACTERIOLOGY
in culture is a eOUUllon characteristic. These ()rganisms
have been found in septic lesions and in gangrenous
conditions of mucous mcmbranes. '1'hey are not
infrequently present in puerperal sepsis and may
produce a blood infection. They have also been
fuunel norlllall V Oil mucous sllrfaces.
The Table oii p. 255 summarises the nwin differential
featnres of the three medically important groups of
aerobic streptococci.
THE PATHOGENICITY AND OCCURRENCE OF
STREPTOCOCCI
The pathogenic effects of the strcptococci depcnd
on the virulenec of the particular strain and the
susceptibility of the host. Thus a strain of low virulence
may produce only a localised inflammation,
whereas strains of high virulence may be associated
with spreading inflammation and even septicaemia.
lIaemolyicic streptococci are found in the following
conditions :-
Wound suppuration; localised abscesscs; spreading
inflammat.ions-e.g. erysipelas, ccllulitis, lymphangitis,
lymphadenitis; septicaemia (e.g. pucrperal
septicaemia) and pyaemia; suppurative otitis and
mastoiditis; meningitis, usually secondary to some
other lesioH-e.g. otitis; lllecmLive endocarditis;
inflammation of the fauces, tonsils, pharynx and
larynx-e.g. acute follicular tonsillitis, the angina of
scarlet fever (vide -inji'[l); broncho-pneumonia secondary
to inftuenza, measles, etc.; peritonitis; lll'inal'Y
sepsis, etc.
In septic lesions, mixed staphylococcal and streptococcal
infcctions are not infrequent.
Streptococci may also occur as secondary invaders
-c.g. in diphtheria, etc.
Non-haemolytic types may occur as pathogens in
lesions of [l, less acute form than those produced by the
haemolytic varieties-e.g. cases of tonsillitis, otitis
media, dental abscesses, brancho-pneumonia, cholecystitis.
Subacute infective endocarditis is due to