144
A. SARAGEA E T AL.
Atypical corynebacteria develop very dry and rough growth, white or
Diphtheroids display white or creamy smooth dense growth.
Tinsdale medium examined with the naked eye, or lens, shows for
C. diphtheriae and C. ulcerans the characteristic black colonies, brownish
halo surround, which might easily be differentiated from all diptheroids
and atypical corynebacteria. These produce black-greyish colonies lacking
the brown halo. The variant with dwarf colonies produces greyish
minute colonies growing tardily (48 h) with a slight, sparse brownish halo.
On blood agar C . diphtheriae shows pearl greyish colonies with a slightly
granular surface, the shape of the colony depending on the type (grauis,
mitis, intermedius) (Fig. 6 ) .
C . ulcerans is very similar to C. dipktkeriae, with smooth yellowish dense
colonies.
Atypical corynebacteria grow after 48 h with rough, dry, often large
colonies, with a silverish white or yellow surface, and deeply crenated
margins (Fig. 32). Usually they are difficult to emulsify and are spontaneously agglutinable.
The variant with dwarf colonies, produces minute silvery colonies with
regular or crenated edges, and a very soft consistency.
Diphtheroids are shiny in surface with dense regular margins.
CTBA medium is the most useful medium for differentiating the
cultural aspects of C. diphtheriae biotypes. At 48 h, differences between all
three types are striking.
Gravis type-large grey to black colonies, granular in surface, with
radial striations and crenated margins (daisy-head-like colonies) (Fig. 3).
Mitis type-intensely black, dense, middle-sized colonies, with regular
margins, convex, shiny-glossy surface (Fig. 4).
Intermedius type-small or middle sized colonies with regular margins,
a granular surface, flat or convex with a raised black centre (Fig. 5).
C. ulcerans develops greyish black dense smooth colonies with a shiny
surface, similar to C. diphtheriae.
Atypical Corynebacterium develops late, after 48 h of incubation with
various sized colonies, intensely black or greyish, dry, with very rough
surface, deeply irregular, crenated edge and raised centre (Fig. 32).
The variant with dwarf colonies of Corynebacterium produces minute
black to brownish colonies, with a slow growth. (Figs 34, 35)
Diphtheroids: C. xerosis displays shiny black colonies, similarly to mitis,
but more smooth in consistency; C. hofmannii shows smooth brownish
colonies (the tellurite incompletely reduced to black metallic tellurium)
which become black in 5-6 days.
C. diphtheriae and C. ulcerans colonies on all solid media show different
yellow in colour, after 48 h.
A. SARAGEA E T AL.
Atypical corynebacteria develop very dry and rough growth, white or
Diphtheroids display white or creamy smooth dense growth.
Tinsdale medium examined with the naked eye, or lens, shows for
C. diphtheriae and C. ulcerans the characteristic black colonies, brownish
halo surround, which might easily be differentiated from all diptheroids
and atypical corynebacteria. These produce black-greyish colonies lacking
the brown halo. The variant with dwarf colonies produces greyish
minute colonies growing tardily (48 h) with a slight, sparse brownish halo.
On blood agar C . diphtheriae shows pearl greyish colonies with a slightly
granular surface, the shape of the colony depending on the type (grauis,
mitis, intermedius) (Fig. 6 ) .
C . ulcerans is very similar to C. dipktkeriae, with smooth yellowish dense
colonies.
Atypical corynebacteria grow after 48 h with rough, dry, often large
colonies, with a silverish white or yellow surface, and deeply crenated
margins (Fig. 32). Usually they are difficult to emulsify and are spontaneously agglutinable.
The variant with dwarf colonies, produces minute silvery colonies with
regular or crenated edges, and a very soft consistency.
Diphtheroids are shiny in surface with dense regular margins.
CTBA medium is the most useful medium for differentiating the
cultural aspects of C. diphtheriae biotypes. At 48 h, differences between all
three types are striking.
Gravis type-large grey to black colonies, granular in surface, with
radial striations and crenated margins (daisy-head-like colonies) (Fig. 3).
Mitis type-intensely black, dense, middle-sized colonies, with regular
margins, convex, shiny-glossy surface (Fig. 4).
Intermedius type-small or middle sized colonies with regular margins,
a granular surface, flat or convex with a raised black centre (Fig. 5).
C. ulcerans develops greyish black dense smooth colonies with a shiny
surface, similar to C. diphtheriae.
Atypical Corynebacterium develops late, after 48 h of incubation with
various sized colonies, intensely black or greyish, dry, with very rough
surface, deeply irregular, crenated edge and raised centre (Fig. 32).
The variant with dwarf colonies of Corynebacterium produces minute
black to brownish colonies, with a slow growth. (Figs 34, 35)
Diphtheroids: C. xerosis displays shiny black colonies, similarly to mitis,
but more smooth in consistency; C. hofmannii shows smooth brownish
colonies (the tellurite incompletely reduced to black metallic tellurium)
which become black in 5-6 days.
C. diphtheriae and C. ulcerans colonies on all solid media show different
yellow in colour, after 48 h.