飲食品の汚染指標としての腸球菌に関する研究-VII : 改良腸球菌検査法

概要

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Although there are several methods for determining the population of enterococci in water and food, no method accurate and reliable from the practical standpoint has yet been established. In order to improve the method for enterococcal test, the author investigated on the selective action of some inhibitory agents and incubation temperature on enterococci medium. From the result of these works, it was shown that high selectivity of confirmatory medium for enterococci can be obtained by the use of some inhibitory agents in combination with incubation temperature at 45°C. Then a new improved method for enterococcal test was devised wherein azide yeast dextrose broth (AYD broth) containing 0.02% sodium azide is used as a presumptive broth and ethyl violet azide citrate broth (EAC broth) containing 0.000012% ethyl violet, 0.025% sodium azide and 1% Na-citrate•2H2O as a confirmatory medium. This method consists of transferring a loopful of culture from a AYD broth tube at 37°C. to a EAC broth tube at 45°C. Since this confirmatory medium, EAC broth is highly specific for enterococci at 45°C., the MPN value of enterococci may in general be determined immediately from the number of positive confirmatory test tubes without laborious procedure in complete test. A modified method in which lactose broth was used in place of AYD broth as presumptive medium in the above-mentioned method was also found to be an excellent one.