Studies on Germination of Spores of Clostridial Species Capable of Causing Food Poisoning (III)

Abstract

The effects of some food additives on the germination of and outgrowth from spores of C. botulinum type E were studied. When germination alone was being studied, it was estimated by measuring the decrease in optical density of spore suspensions in a chemically defined medium (ALB) consisting of 5mM L-alanine, 10mM sodium lactate, 60mM sodium bicarbonate, and 100mM phosphate buffer, pH 6.7. When both germination and outgrowth were being studied, they were followed by measuring the decrease and subsequent increase in optical density in a complex medium consisting of 3.0% thiotone, 0.4% glucose, 0.1% sodium thioglycollate, 50mM phosphate buffer, pH 6.7, and 0.1% sodium bicarbonate. The results are summarized as follows:1) Sodium chloride concentrations up to 5% progressively reduced the rate of germination and finally inhibited germination.2) Sodium nitrite at higher concentrations (more than 1%) inhibited germination altogether. On the other hand, nitrite alone as much as 2-4% stimulated germination of unheated spores at pH 6.3) Nitrite concentrations of less than 0.1% allowed germination, but arrested further outgrowth subsequent to germination in the thiotone medium. A concentration of 0.05% nitrite was required for preventing outgrowth in the presence of 0.5% NaCl. The addition of 0.05% nitrite before autoclaving the medium was effective for preventing outgrowth, as compared to the outgrowth obtained when nitrite was added after autoclaving.4) Potassium sorbate had no apparent effect on germination and outgrowth at concentrations of less than 0.5%, although as much as 1% sorbate reduced the rate and extent of germination to some extent.5) Furylfuramide could not inhibit germination at even greater than commercially acceptable concentrations. Neverthless, the compound inhibited outgrowth at 10ppm but not at 5ppm.