TOXIC EFFECT OF GLUCOSE ON VIRULENT PASTEURELLA PESTIS IN CHEMICALLY DEFINED MEDIA

Abstract

Five virulent strains of P. pestis cultivated at 37[degree]C in a chemically defined medium containing glucose as the energy source, undergo a reduction in viable count, then recover and grow in a logarithmic manner. Two glycerol-fermenting virulent strains and seven avirulent strains produce normal growth curves. The reduction in count is caused by death and lysis of the cells; it is not apparent when other energy sources are used, and does not occur at temperatures below 37oC. Addition of relatively large amounts of Mn++ or Mg++ to the medium prevent or reduce the decrease in viable count. Those organisms which grew after the culture had undergone a reduction in count were titrated for virulence at various stages of growth; they were found to become progressively less virulent, except when the initial pH is above 7.8. The loss in virulence is attributed to growth of avirulent mutants.