BACILLUS AMINOPHILUS 401 
A closely related organism, B. acidi lactici, is found fairly widely dis- 
tributed in milk, water, and sewage. A sharp differentiation between 
the two organisms is difficult to establish. There is evidence that 
the organism, ordinarily a harmless intestinal parasite, may become 
temporarily pathogenic and incite intestinal disturbance varying in 
intensity from slight diarrhea to severe enteritis.^ Occasional cases 
of cystitis in infants are also associated with the presence of B. lactis 
aerogenes in pure culture. 
It is obvious that the interrelations of the mucosus capsulatus group 
are at present in an unsatisfactory state— attempts to separate the 
organisms on the basis of serological reactions have been unsuccessful, 
partly because of the difficulty of removing the capsules which appear 
to be somewhat impervious to antibodies. A final arrangement of 
the group and an ultimate differentiation of the various organisms 
comprising it awaits future elucidation. 
Bacillus Aminophilus. — Berthelot and Bertrand- have described an 
organism apparently belonging to the mucosus capsulatus group, 
which possesses the morphology and staining reactions of the pneumo- 
bacillus. Capsules have not been described. It is non-motile, and 
possesses no flagella. 
The noteworthy characteristic of some strains of this organism 
resides in their ability to transform considerable amounts of histidine 
to the corresponding amine by the elimination of COo. 
-NH HC NH 
CH 
CH 
C N -^ C N + CO2 
I I 
CH2 CH2 
I I 
CHNH2 CH2NH2 
I 
COOH 
Histidine. Histamine, or beta-imidazole ethylamine. 
It is not definitely proven that other members of the mucosus capsu- 
latus group may not form histamine, however. The chief interest sur- 
rounding B. aminophilus at the present time lies in the formation 
of the physiologically active histamine, and the conditions under which 
this takes place. Berthelot^ has studied the effects of diet containing 
B. aminophilus and B. proteus upon rats, and has apparently succeeded 
in inducing a mucous diarrhea, which is attributed to the summation 
of activity of the two organisms. 
It is inferred by him that certain poorly defined diarrheas of infancy 
and childhood may be similarly referred to the proteus-aminophilus 
symbiosis. 
1 Kendall and Day: Boston Med. and Surg. Jour., 1913, 169, 753. Kendall: Ibid., 
May 20, 1915. 
- Compt rend. Acad. Sci., 1912, 154, 1643, 1826. 
3 Ann. Inst. Pasteur, 1914, 28, 132. 
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