AGf~ICULTURAL RESEARCH, PUSA.

CHAPTER XI
BACILLUS DIPH'l'HERIAE AND BIO­
LOGICALLY ALLIED ORGANISMS;
B. PSEUDO-TUBERCI1LOSIS OVIS
AND BACILLUS OF EQUINE
ULCERATIVE L YMPHANGl'l'IS ;
BACILLUS PYOGENES
BACILLUS DIPHTHERIAE (Corynebacterium diphthcl'iae,
Klebs-Loffler bacillus)
'fIlE causative organism of diphtheria.
Morphology and Staining. - Slender rod - shaped
organism, st.raight 01' slightly curved; the average
size is 8/1. by 0 ·8p., but longer and shorter forIllS may bc
noted; the ends are often swollen; it is non-motile
and non-sporing. In culture, involution forms may
be observed which are pear-shaped, club-shaped, 01'
even globular. The bacillus is Gram-positive, though
more readily decolorised than many other Grampositive
organisms; stained with methylene blue it
shows marked "beading," and by N eisser's method
(vide p. 160) metachromatic granules are characteristic,
staining blue-black in contrast with the light-brown
coloration of the rest of the organism; the granules
arc often polar in situation. If over-decolorised in the
Gram method the granules tend to retain the violet
stain, while the rest of thc organism is decolorisecl.
These characteristic staining reactions may bc elicited
in culture only whcn the bacillus is grown on a :serum
mediulll.
Cullure.-Aerobc; temperature range-20°-40° C.,
optimum-37° C.; grows on ordinary nutrient media,
but best on serum media.
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