IV. INVESTIGATION OF C. DIPHTHERIAE
143
Stock cultures on Loeffler slants are tested for:
(a) Microscopical morphology. Gram stained smears show slender, slightly
club-shaped, pleomorphic bacilli, arranged like Chinese letters ; granular
bodies and club forms are recognised by their intense violet staining in
contrast with the C. diphtheriae bacillus which in Gram staining is easily
decolourised (Fig. 1).
When Neisser or del Vecchio staining are used, brownish green metachromatic granules (Babes-Ernst bodies) on a yellowish green background
of the bacillary body are observed.
After Methylene blue staining, reddish metachromatic granules appear
in the blue bacillary bodies.
C . ulceram shows predominantly pleomorphic cocci (very easily decolourised) (Fig. 25) and sometimes rod forms similar to those of C.
diphtheriae.
Atypical corynebacteria show long, apparently branched club-shaped
bacilli, with large Babes-Ernst bodies (Fig. 31).
The dwarf colony variant of Corynebacterium shows minute, short,
slender rods, with rare corpuscules, Gram-positive at the ends.
Diphtheroids are intensely Gram-positive and show short rods with
pointed ends, regularly arranged in palisades (C. hofmannii, Fig. 27), or
intermediary irregular staining rods, slightly similar to C. diphtheriae (C.
xerosis, Fig. 30).
(b) Growth characters
accordingly to the type :
liquid.
(i) I n broth, C. diphtheriae develops different features of growth,
gravis: pellicle on the surface, deposit on the bottom, leaving a clear
intermedius: granular culture and deposit on the walls and at the bottom.
mitis: slightly homogeneous turbidity.
C. ulcerans resembles gravis, mitis or intermedius C. diphtheriae.
Atypical corynebacteria : white or yellow coarse pellicle on the surface,
Dwarf colony variant of Corynebacterium, grows only at the bottom with
Diphtheroids show a uniform heavy turbidity.
(ii) On solid media on Loeffler, C. diphtheriae develops with a creamy
coloured, smooth or granular culture ; C. ulcerans grows similarly, but with
more luxuriant growth. The variant with dwarf colonies show a granular,
slow, sparse growth.
thick deposit on the bottom and clear liquid.
no turbidity in the liquid.
143
Stock cultures on Loeffler slants are tested for:
(a) Microscopical morphology. Gram stained smears show slender, slightly
club-shaped, pleomorphic bacilli, arranged like Chinese letters ; granular
bodies and club forms are recognised by their intense violet staining in
contrast with the C. diphtheriae bacillus which in Gram staining is easily
decolourised (Fig. 1).
When Neisser or del Vecchio staining are used, brownish green metachromatic granules (Babes-Ernst bodies) on a yellowish green background
of the bacillary body are observed.
After Methylene blue staining, reddish metachromatic granules appear
in the blue bacillary bodies.
C . ulceram shows predominantly pleomorphic cocci (very easily decolourised) (Fig. 25) and sometimes rod forms similar to those of C.
diphtheriae.
Atypical corynebacteria show long, apparently branched club-shaped
bacilli, with large Babes-Ernst bodies (Fig. 31).
The dwarf colony variant of Corynebacterium shows minute, short,
slender rods, with rare corpuscules, Gram-positive at the ends.
Diphtheroids are intensely Gram-positive and show short rods with
pointed ends, regularly arranged in palisades (C. hofmannii, Fig. 27), or
intermediary irregular staining rods, slightly similar to C. diphtheriae (C.
xerosis, Fig. 30).
(b) Growth characters
accordingly to the type :
liquid.
(i) I n broth, C. diphtheriae develops different features of growth,
gravis: pellicle on the surface, deposit on the bottom, leaving a clear
intermedius: granular culture and deposit on the walls and at the bottom.
mitis: slightly homogeneous turbidity.
C. ulcerans resembles gravis, mitis or intermedius C. diphtheriae.
Atypical corynebacteria : white or yellow coarse pellicle on the surface,
Dwarf colony variant of Corynebacterium, grows only at the bottom with
Diphtheroids show a uniform heavy turbidity.
(ii) On solid media on Loeffler, C. diphtheriae develops with a creamy
coloured, smooth or granular culture ; C. ulcerans grows similarly, but with
more luxuriant growth. The variant with dwarf colonies show a granular,
slow, sparse growth.
thick deposit on the bottom and clear liquid.
no turbidity in the liquid.