A survey of the literature lias shown that
Actinobacillus lirenieresi has not been well
characterised, its identification being dependent, in
part, upon its association with typical actinomycotic
lesions. Because of this, the existence of the
commensal form of the organism has been suspected but
never proven,The morphological, cultural and biochemical
characters of 220 strains of A, lignieresi isolated
from pathological material have been investigated, A
distinctive feature was the production of granules
which, in conjunction with the bacilli themselves,
gave a characteristic arrangement which has been named
the "Morse code" form. A number of fermentable
substrates were constantly fermented and others were
consistently not attacked, whilst several substrates
gave varying results with different strains. Several
biochemical tests which have been shown to give
constantly negative or positive results, can also be
used for identification. An hitherto unrecorded
character of A, lignieresi that has been demonstrated
is the ability of many strains to synthesise starch
from dextrose and maltose.Th.e antigenic structure of 218 strains of
A. lignieresi was investigated by slide and tube
agglutination tests and absorption tests. Six
antigenic types (no. 1-6) and two subtypes (la, 4a) of
organisms were distinguished by differences in their
heat-stable antigens; 203 of the strains were
classified in these types and 15 were untyped. The
majority of strains isolated from cattle belonged to
type 1 and most of those from sheep to types 2, 3 and
4.Heat labile antigens common to different antigenic
types were found in living and formaldehyde-killed
organisms. These antigens may be responsible for
inagglutinability of living organisms tested with
antisera to the heat-stable antigens. The heat-labile
antigenic material appeared to be associated with
extracellular slime produced in small amounts by the
organism.A medium containing oleandomycin and nystatin has
been developed for the isolation of actinobacilli from
mixed bacterial populations. Its use resulted in the
isolation of organisms resembling A. lignieresi in
morphological and biochemical characters from the
ruminal contents of normal cattle and sheep and from
the tongues of normal cattle. The organisms from
normal animals showed an antigenic relationship with
the pathogenic strains.Antibodies to A. lignieresi have been demonstrated
in sera from normal adult cattle in titres up to 1 in
l60. Very young calves, however, were shown not to
possess such antibodies but to acquire them gradually
during their first year of life. Antibodies to
A. lignieresi in the sera from normal sheep were found
at slightly higher levels than in cattle.The value of the agglutination test as a
diagnostic procedure for clinical actinobacillosis has
been investigated. Most sera from clinically affected
cattle and from slaughterhouse cases of the disease
showed higher levels of antibody than normal animals
and the occurrence of a prozone in tests with such
samples was a notable feature which was absent in tests
with sera from normal animals.The relationship of Bacterium equirulis
(Actinobacillus equuli) to A, lignieresi has been
investigated. Similarities were apparent in the
morphological, cultural, biochemical and antigenic
characters
