218
IMPROVED
salmonella antigen,
ETC.
[Vol. XXII, Part III
a single strain of S. pullorum containing the full complement of XII 2 factor, variants
being few in the prevailing strains examined in England. An antigen, containing
three standard and two yonie (variants) strains, is used in Canada as the prevalence
of the three components of XII factor [Edwards and Burner, 1946] and their quan-
titative Variants especially. of XII 2 amongst the strain's isolated has been recognised
[Gwatkin, 1945 and Gwatkin and Bond; 1945]. Lately, an effort is being made
to incorporate a strain or strains of S. pullorum containing both XII 2 and XII 3
antigenic components [Van Roekal, 1950]. Experimental work has also been
directed to increase the agglutinability and secure a higher yield of the organism
on special media like the Veal infusion agar enriched with glycerine and sulphur
[Macdonald 'K' antigen, 1946], or glycerine and sodium-thiosulphate as used by
Weybridge Poultry Department Laboratories [Dobson, 1950].
A review of literature since Bunyea, Hall and Dorset [1929] applied the whole
blood test for detection of pullorum carriers, reveals a diversity of views both as
regards the. method and accuracy though the trend of research has been towards
increasing the efficiency by improving the specificity, agglutinability and keeping
qualities of the antigen.
Edwards and Hull [1929] have reported that even slide serum tests were not
satisfactory in birds whose end titres were lower than 1 to 80. In most laboratories
the diagnostic titre is 1 to 40; and in some 1 to 20 for the hen and 1 to 10 for the
cock [Gaiger and Davis, 1946].
Lubbehosen and Beach [1935] and Hinshaw, Harr and Niemeyer [1940] con-
sidered the test was not efficient enough to be used exclusively, while Stafseth [1938],
Reid [1938] Barger and Torry [1933] and Winter [1939] recorded goods correlation
between the tube and plate tests.
Linn, Leask, Gunderson and Slack [1944] concluded that the routine standard
'spot' antigen then in vogue in the U. S. A. would detect titres as low as 1 to 10 in
the majority of cases and was superior to Macdonald's 'K' antigen [1941], grown on
special media for detecting low titre birds. Gordon [1947] has recorded very close
agreement between the whole blood spot and the tube tests with the alcoholic
antigen now in use in England.
Diverse views and methods of the workers show that antigens vary in sensitivity;
yet when a suitable one is used the results closely agree with the tube tests. To
obtain further information on the subject it was found necessary to compare and
select, from the available information, the one that could make finer distinctions in
the reading of doubtful reactions, and adapt it for use so that there might be unifor-
mity in testing birds all over this country.
EXPERIMENTAL
Material and Methods. As a preliminary work the following antigens were selected
for comparison with the one locally produced, herein called Experimental No. 3.
1. Antigen of Schaffer et al. [1931].
Culture media. Beef infusion agar pH 7.2 incubated for 72 hours at 37.5°C.
Suspending fluid 1 per cent formaline (0.4 per cent actual formalde-
hyde in 0.85 per cent sodium chloride solution) Dye used. Crystal
violet 1 per cent solution, 3 c.c. per 100 c.c. of antigen.