The Use of the Selective Inhibitory Action of Toluene on Coliform Bacilli in Routine Cultures.

Benians (1913) demonstrated that all Gramnegative organisms were destroyed by toluene, which had an inhibitory action on diphtheroid bacilli and streptococci but little effect on spores and staphylococci. Webster (1942) suggested the use of toluene to suppress Gram-negative bacilli in mixed broth cultures; he added 10 per cent of toluene to broth cultures, shook them at intervals, and allowed them to stand for five minutes, by which time the toluene had risen to the surface. He removed a drop of the treated culture, taking precautions to avoid removing any toluene. Using this technique we have obtained results too variable to be of value, as sometimes coliform bacilli would survive or streptococci succumb. " Occasional" shaking is too haphazard, but vigorous shaking gives consistent results so long as the temperature of the broth is controlled.