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A. SARAGEA ET AL.
FIG. 5 . C. diphtheriae type intermedius colonies on CTBA plates.
colour, with granular or shiny surface, with crenated or regular edges;
(Fig. 6) they are friable or butyrous.
On Loefler slants, the granular culture is white, pale or deeper cream in
colour, butyrous in consistency and easily emulsifiable in saline; it sometimes shows spontaneous agglutination.
On nutrient broth growth readily occurs. Type gravis: veil on surface and
a small deposit at the bottom, the remaining broth clear. Type mitis:
homogeneous, slightly turbid. Type intermedius: granular deposit on the
walls and at the bottom.
5 . Enzymes
(a) Cystinase. Hydrogen sulphide production from cystine is one of the
most characteristic enzymatic features of C. d$htheriae (Pisu and Guarnacci, 1971). Cystinase is produced also by C . zilcerans and C. ovis. This
enzyme is not to be found in any other of the diphtheroids.
(b) Glycoside hydrolases. A general characteristic of almost all members of
the group is production of acid from carbohydrates without gas. C.
hofmannii is the only member of the group which does not split any
carbohydrate. Glycoside hydrolases are very important “markers”, useful
for the diagnosis of the type species of C. diphtheriae, as well as its biotypes,
A. SARAGEA ET AL.
FIG. 5 . C. diphtheriae type intermedius colonies on CTBA plates.
colour, with granular or shiny surface, with crenated or regular edges;
(Fig. 6) they are friable or butyrous.
On Loefler slants, the granular culture is white, pale or deeper cream in
colour, butyrous in consistency and easily emulsifiable in saline; it sometimes shows spontaneous agglutination.
On nutrient broth growth readily occurs. Type gravis: veil on surface and
a small deposit at the bottom, the remaining broth clear. Type mitis:
homogeneous, slightly turbid. Type intermedius: granular deposit on the
walls and at the bottom.
5 . Enzymes
(a) Cystinase. Hydrogen sulphide production from cystine is one of the
most characteristic enzymatic features of C. d$htheriae (Pisu and Guarnacci, 1971). Cystinase is produced also by C . zilcerans and C. ovis. This
enzyme is not to be found in any other of the diphtheroids.
(b) Glycoside hydrolases. A general characteristic of almost all members of
the group is production of acid from carbohydrates without gas. C.
hofmannii is the only member of the group which does not split any
carbohydrate. Glycoside hydrolases are very important “markers”, useful
for the diagnosis of the type species of C. diphtheriae, as well as its biotypes,