Abstract
The survival or growth of tubercle bacilli in blood is an important question from several points of view: the immunological action of serum and leucocytes, the investigation of tuberculous bacillemia, and the suitability of blood as a culture medium. Some investigators have emphasized the unfavorable action of blood on the growth of tubercle bacilli on solid media, while others have reported the growth of these organisms in blood. These points of view were reconciled when it was learned that the influence of blood in the two situations is quite different. This note indicates that, although blood interferes with the growth of tubercle bacilli on a solid substrate, it is actually an excellent medium.
Saline, defibrinated rabbit blood, or serum, .45 cc, were mixed with .05 cc volumes of 4 decimal dilutions of “clump-free” suspensions of human, bovine, avian, and timothy bacilli in 10 × 75 mm Pyrex tubes. Of these mixtures .05 cc was spread evenly on each of two slants of Corper's egg-yolk medium (in screw-capped tubes) which were free of surface moisture. The small tubes containing the mixtures were sealed with paraffined corks; both solid and liquid mediums were incubated with their surfaces horizontal.
From the results in Table I, several conclusions may be drawn: (a) Rabbit blood and serum were as favorable as the solid medium, with two exceptions: the irregular growth of bovine bacilli in blood, and the delayed growth of timothy bacilli in serum. (b) There was no evidence of the growth-inhibitory effects hitherto ascribed to hemoglobin or to “autolytic products” of blood. (c) The failure of tubercle bacilli to grow suitably on solid medium inoculated with blood was again confirmed. Positive results cannot be obtained with small numbers of bacilli.
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