Basic studies on the viability of El Tor vibrios.

Quantitative data are presented on the viability of El Tor vibrios in various foodstuffs under different conditions. El Tor vibrios were found to have a very short life in water at -20 degrees C, but in various nutrient media, such as skim milk, sugar solution or meat extract, they could live for more than a month at this temperature; the survival rate was always much higher when the vibrio suspension was cooled rapidly to -72 degrees C and stored at this temperature.The optimum pH for the growth and survival of El Tor vibrios is 6-8, and the optimum osmotic pressure 250 mOsm-700 mOsm. The resistance of El Tor vibrios to disinfectants is lower than that of salmonellae and Escherichia coli. The El Tor vibrios are more resistant than classical cholera vibrios to such disinfectants as benzethonium chloride and o-dichlorobenzene. They are not resistant to sodium hypochlorite or bleaching powder at 6 ppm.The results of the investigation emphasize the necessity of immediate and proper disinfection of foodstuffs contaminated with El Tor vibrios, and indicate the possibility of survival of the organisms for long periods under favourable conditions.