176
Bacteriology of Bovine Mastitis in India
Haemolysis. Str. agalactiae was easily recognized,
by the comparatively small width, and weak charac-
ter of the ß-haemolytic zones about the deep colonies
in ox-blood agar plates after 24 hours incubation.
Growth. Growth in one or 5 per cent serum broth
was moderately abundant, with clear supernatant
and floccular sediment, sometimes faintly pigmented.
The sediment was composed of medium to long chains
of Gram-positive cocci.
Hydrolysis of sodium hippurate. This reagent
was unmistakably hydrolysed (usual ferric chloride
test, with unsown hippurate broth controls).
Final pH in one per cent glucose broth. This was
generally low, towards 4.2.
Litmus-milk. Fair inocula produced rapid acidity
with firm clot formation within 24 hours, with some
decolourization at the bottom. On further incu-
bation, a clear reddish whey was expressed.
Methylene blue-milk. Generally, the results varied
with the size of the inoculum. Small inocula failed
to grow. Heavy inocula caused a complete reduction
and clot formation within 24 hours, followed later
by progressive oxidation from the top.
Sugar reactions. All strains produced acid in
lactose, sucrose, salicin and trehalose, but not in
mannitol, sorbitol, raffinose and inulin.
(b) Str. uberis. Str. uberis (Mastitis Streptococcus,
Group III, of Minett et al.) was isolated from two
cows at Mukteswar. Both were α-haemolytic, gave
abundant floccular growth in serum broth with
clear supernatant, formed short to medium chains,
hydrolysed sodium hippurate, produced a final
pH 4.6-4.9 in glucose broth, acid in litmus-milk
with small inocula but acid and soft clot within 24
hours with larger inocula, acid in lactose, sucrose,
mannitol, salicin, sorbitol, trehalose and inulin,
but not in reffinose.
(c) Str. dysgalactiae. Str. dysgalactiae (Mas
titis Streptococcus, Group II, of Minett et al.) was
suspected in one cow at Mukteswar, but the reactions
were not quite typical. Except for the type of
haemolysis, these characters were not very different
from those manifested by strains labelled as Str.
subacidus. The organism was α-haemolytic, grew
abundantly in serum broth as a floccular pigmented
sediment with clear supernatant, short to medium
chains, a final pH of 5.4 in glucose broth, no hydro
lysis of sodium hippurate, acid in sucrose and tre-
halose. Small inocula in litmus-milk and methylene
blue-milk gave no change, larger inocula caused
a slight and incomplete reduction later returning
to normal.
(d) Str. subacidus. This was the label given to
a number of strongly ß-haemolytic streptococcus
strains isolated from various cows at Mukteswar
and elsewhere, sometimes repeatedly and in large
numbers, and often in association with Staph. pyo-
genes. These streptococci were considered to be
definitely pathogenic and their main cultural and
biochemical characters were as follows: typical
streptococcus colonies, both deep and superficial
ones being surrounded by wide zones of clear ß-
haemolysis; abundant and sometimes pigmented
floccular sediment and clear supernatant in serum
broth, chains of medium length; final pH of 5.2—
5.6 in glucose broth ; hippurate not hydrolysed ;
acid and slowly-formed incomplete clot in litmus-
milk with slight reduction at bottom ; small inocula
producing no change in methylene blue-milk but
larger inocula causing complete reduction with clot
formation; acid only in lactose, sucrose, and
trehalose.
Two of these strains were tested for pathogenicity,
using 0.5 c.c. serum broth culture intraperitoneally.
Both were non-pathogenic at this dose.
(e) Str. acidominimus. Twenty-five strains, iso-
lated from ten cows at Mukteswar, had the charac-
ters of this species. There was no evidence of mastitis
in these cows and the streptococci appeared
to be saprophytic. Their salient characters were:
alpha-haemolysis ; slight uniform turbidity in serum
broth, short to medium chains ; final pH. 6.6 in
glucose broth ; comparatively weak but definite
hydrolysis of sodium hippurate ; no change in litmus-
milk or methylene blue milk ; very weak acid in
lactose, surcrose and trehalose,
(f) Unclassified. Seventy-three strains isolated
from 56 cows could not be properly classified. Most
were considered of no direct pathogenic signifi-
cance.
2. Staphylococci, These commonly found orga-
nisms were divisible into two main groups [Minett,
1937].
(a) Saprophytic staphylococci. (i) Colonies un-
pigmented or white pigmented, superficial ones
often resting on a bed of clear haemolysis but deep
colonies either non-haemolytic or surrounded by
zones of greenish discolouration ; (ii) Colonies pig-
mented yellow or somewhat like 'Staph. aureus'
or, as in one case only, like ' Staph. citreus ', generally
with no evidence of haemolysis around either deep
or superficial ones ; (iii) Small colonies, the deeper
ones more minute and often surrounded by fair-
sized zones of intense greenish discolouration.
Organisms of the last group had a characteristic
tendency to form tetrads. In ox-blood agar plates,
their minute deep colonies were sometimes liable
to be mistaken for streptococcus colonies. The
few strains studied of these different types were
found to be non-proteolytic and failed to form coa-
gulase or soluble haemolysis.
(b) Staph. pyogenes. Colonies generally pigmented
like ' Staph. aureus '. Deep colonies were surrounded
(i) in several cases, by wide and well-defined zones
of darkening, characteristic of ß-toxin ; (ii) in a few
cases, by moderate-sized zones of clear haemolysis,