AGf~ICULTURAL RESEARCH, PUSA.

276 PRACTICAL BACTERIOLOGY
The final identification is carried out by means of a
polyvalent agglutinating anti-m.eningococcus serum or
antisera to the differcnt types.
THE GRAM-NEGATIVE DIPLOCOCCI OCCURRING
AS COMMENSALS IN THE NOSE AND THROAT
DIPLOCOCCUS CATARRHALIS (Neisseria cata1'1'halis)
A frequent commensal in the throat and nose,
and often regarded as pathogenic in catarrhal inflammations
of the respiratory tract .
.l.1101phology and Staining.-Practically identical ·with
the meningococcus.
C1Iltut·e.-Grows on ordinarv media without serum;
grows at room temperature; . the colonies are usually
larger than those of meningococcus, especially whcn
fully grown, thicker and more opaque, and exhibit a
somewhat tough consistence, so that they can actually
hc moved ahout on the medium with a platinum loop
without lJcing broken up. 'The colollY charactcrs may
vary considerably from the features described above.
The organism exhibitH no fermentative properties
(vide infra).
D. caial'i'lwHs is not agglutinated by mcningococcus
antisera.
DIPLOCOCCUS FLAVUS TYPES (e.g. Neisseria (lava)
The mm'phology of thesc organisms is like that of
D. {:atarrlwlis, and they grow on ordinary media at
rOOlll temperature. Cultures develop, after fortyeight
hours, greenish-yellow or greenish-grey colours.
Young colonies may simulate closely those of thc
meningococcus.
Biochem-tcal -react'ions, which vary according to the
type, are shown in the Table on p. 277.
'They arc llot agglutinated specifically by meningococcus
antisera, but may agglutinate in low dilutions
of horse serum. This has to be remembered in
identifying meningococci from carriers when antisera
from horses a.re used for the serological test.