THE DIFFERENTIATION OF PRIMARY ISOLATIONS OF 
BACTERIUM MELITENSIS FROM PRIMARY ISOLATIONS 
OF BACTERIUM ABORTUS (BOVINE) BY THEIR CUL¬ 
TURAL AND ATMOSPHERIC REQUIREMENTS 1 
By John M. Buck 
Pathological Division, Bureau of Animal Industry, United States Department of 
Agriculture 
INTRODUCTION 
That the resemblance of Bacterium 
abortus to Bad. melitensis in morphologi¬ 
cal, cultural, biochemical, and serologi¬ 
cal respects is so close that their 
differentiation is difficult if not well- 
nigh impossible was discovered by 
Alice C. Evans (6) z in 1918, and later 
confirmed by Feusier and Meyer (5). 
This has led investigators to wonder 
whether the likeness in the two 
organisms ceases with form, action, and 
appearance upon artificial culture media 
and serological characteristics, or in¬ 
volves pathogenicity as well. Investi¬ 
gations bearing upon pathogenicity 
made later by Fleischner, Vecki, Shaw, 
and Meyer ( 9) indicate that the 
similarity even with respect to patho¬ 
genicity may be less remote than 
formerly suspected. Further informa¬ 
tion on this phase of the subject has 
been contributed by Khaled (18), 
Huddleson (16), Evans (7), and others. 
In view of the fact, however, that 
severe illness in humans has never been 
definitely traced to the ingestion of 
Bacterium abortus in milk, few investi¬ 
gators have considered the two organ¬ 
isms identical; and the practice of 
utilizing milk containing this microor¬ 
ganism is far too general to permit 
ignoring the great quantity of available 
evidence thereon. Comparative studies 
of Bad. abortus and Bad. melitensis 
seem to have been mainly confined to 
strains which have been under artificial 
cultivation for considerable periods of 
time and are well accustomed to propa¬ 
gation upon artificial media rather than 
to those of recent isolation. 
During 1922 and 1923 the writer had 
opportunity to make comparisons of 
some recently isolated strains of the 
two types of organisms. Results of 
this work seem to indicate that by 
cultural methods Bacterium melitensis 
and Bad. abortus (bovine) may be 
readily distinguished during their pri¬ 
mary isolations. 
The cultural results differed but little 
from those anticipated. Investigators 
of Malta fever have written little if at 
all of special or unusual biological 
requirements of the Malta fever organ¬ 
ism, whereas in bovine infectious 
abortion the peculiar cultural char¬ 
acteristics of Bacterium abortus seem to 
have been the factor which retarded its 
discovery. The originality manifested 
by Bang and Stribolt (1) in their 
successful cultural work with Bad. 
abortus has never ceased to receive the 
profound respect which it rightfully 
deserves. 
EXPERIMENTS AND RESULTS 
During August, 1922, 24 samples of 
blood serum from goats suspected of 
being affected with Malta fever were 
forwarded to the Pathological Division, 
Bureau of Animal Industry, by Dr. W. 
A. Heck, a practicing veterinarian of 
Donna, Hidalgo County, Tex. When 
the samples were subjected to the ag¬ 
glutination test for this disease, four 
reacted in a dilution of 1 to 1,000, one 
1 to 500, seven 1 to 200, two 1 to 100, 
one 1 to 50, and one 1 to 25. Eight 
gave negative results to the test in a 
dilution of 1 to 25 or higher. About a 
month before these samples arrived, 
T. B. Hooks, of Donna, Tex. (owner of 
the animals), had inquired if any test 
could determine whether the goats were 
affected with Malta fever. He stated 
in the communication that his brother, 
who had been using milk from this flock, 
had been suffering six months with some 
kind of fever suspected of being Malta 
1 Received for publication June 3, 1924; issued March, 1925. 
2 Reference is made by number (italic) to “Literature cited,” pp. 590-591. 
Journal of Agricultural Research, 
Washington, D. C. 
(585) 
Vol. XXIX, No. 12. 
Dec. 15, 1924 
Key No A-86 
