Abstract
Strains (38) of a Gram-positive bacterium identified as B. licheniformis var. endoparasiticus (Benedek), referred to as BLE, were isolated in various stages of reversion from the L-forms, from 28 out of 100 samples of whole blood or erythrocytes from normal healthy subjects, after prolonged incubation. Similar results were obtained from 100 samples from hospital patients with conditions not usually associated with blood infection. BLE was isolated from only 1 of 125 samples of plasma, including those separated from infected erythrocytes. Isolates from cultures incubated for up to 4 mo. were usually in the form of spheroplasts of diphtheroid bacilli; the fully reverted phase, resembling B. licheniformis, with the capacity to form endospores, was isolated occasionally from cultures aged 1-6 mo. and it constituted about half the isolates recovered from cultures aged 6-25 mo. BLE was isolated in subculture, and with the usual frequency, in previously unopened, primary cultures. It did not occur in 1200 subcultures of 150 control cultures made with autoclaved or irradiated blood cells; it was not detected in the environment of the laboratory or blood-sampling areas, or on the skin or in the respiratory passages of the operators and other persons associated with the laboratory, where typical, saprophytic B. licheniformis was very rare. This Bacillus sp. exists as an L-form, associated with the erythrocytes of a large proportion of normal persons, as previously recorded by several observers. Some of the morphological variants associated with the L-cycles have in the past been described as different organisms, for example L-forms of various bacteria or mycoplasmas, and the diphtheroid stage was thought to belong to the genera Corynebacterium and Listeria. The sporogenous stage, although frequently described, is normally discounted as a contaminant. These observations do not admit of any conclusion in respect of the claims that such bacteria may have a role in arthritis, cancer or other diseases.