Abstract
A strain of B. histolyticus (No. 141) received from the Pasteur Institute in Paris in March, 1921, and described by me 1 last year, was recently found capable of repeated and successive aerobic culture upon the surface of meat infusion and blood agar slants without resort to any method of reducing the oxygen pressure. The accuracy of this observation is guaranteed not alone by the unique pathogenicity, but as well by the particular combination of morphologic and cultural properties of this species which enable one to identify it without reference to its oxygen requirements.
All authors dealing with B. histolyticus have regarded it as an obligate anaerobe and my own previous failure to observe aerobic growth can only be explained by my reliance upon meat extract, instead of meat infusion, agar slants, for detecting aerobic growth until recently. Even the growth upon meat infusion agar is extremely delicate and might be easily overlooked by any but a highly critical dye. My first supposition upon observing the delicate transparent aerobic growth upon a meat infusion blood agar slant was that a contamination had occurred. This assumption was clearly denied when as many as 31 successive transplants of this culture were made upon blood and plain meat infusion agar during a period of about 60 days without altering any of its morphologic, cultural or pathogenic characteristics permanently; there were temporary differences observed, however, in the morphology of the first few aerobic cultures, but later transplants appeared to be identical in every way with a corresponding strain cultured anaerobically in brain medium.
The possibility of contamination was also excluded by finding no significant differences in well separated deep agar colonies and in the observation that subcultrrres from such deepcolonies may also he grown aerobically.
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