Influence of Carbohydrates on In Vitro Production of Enterotoxin by Food Poisoning Strains of Clostridium perfringens

抄録

Sporulation and enterotoxin production of food poisoning strains of Clostridium. perfringens type A in sporulation media containing carbohydrates were investigated. A slightly modified Duncan and Strong sporulation medium (BM1) and one without soluble starch (BM2) were employed as basal media. BM1 consisted of proteose peptone (1.8%), yeast extract (0.2%), sodium thioglycolate (0.05%), dibasic sodium phosphate (Na₂HPO₄·12H₂O, 1.2%) and soluble starch (0.4%).
1. From our stock cultures involved in food poisoning outbreaks, strain NCTC8239 with a normally high sporulation frequency and strain A76 with a low sporulation frequency were chosen and the effect of carbohydrate on sporulation and enterotoxin production of those strains was compared with that of soluble starch. Results were as follows: (a) Strain NCTC8239. Fructose and raffinose (+, more effective than soluble starch), lactose and galactose (±), glucose and sucrose (-, less effective than soluble starch); (b) Strain A76. Fructose, galactose, raffinose and sucrose (+), lactose (±), glucose (-).
2. Each of strains NCTC8239, NCTC8798, S79, A75 and A76 showed approximately the same level in spore numbers in BM2 supplemented by galactose or fructose. As to the amount of enterotoxin determined, however, fructose was more effective than galactose. All strains tested produced more than 24μg/ml of enterotoxin in BM2 containing fructose at 1%.
3. The pH value of the final cultures in BM1 was between 5.1 and 6.6, where a satisfactory amount of enterotoxin was determined. But, a maximum in enterotoxin production in BM1 and BM2 supplemented by a carbohydrate other than glucose was obtained when the pH value of the final culture dropped to between 5 and 6. This range of pH value was easily achieved by reducing the concentration of glucose, but no detectable amount of enterotoxin was yielded in the glucose-containing media. Increasing the concentration of soluble starch in BM2 up to 1.6% did not always result in an increase in the amount of enterotoxin produced.