The evaluation of effects of nitrite, PH, salt, temperature and storage of time on growth and toxigenesis of Clostridium botulinum type A in BHI model.

In this study, the interference in interaction between intrinsic and extrinsic parameters including nitrite, pH, salt, temperature and storage time on growth and toxigenesis of Clostridium botulinum type A, has been examined during three steps. In the first step, sporogenesis of Clostridium botulinum type A was done on Egg yolk Agar and spore count in one milliliter of suspension was obtained.In the second step, the turbidity time with inoculation level of 4×104 spore in each milliliter of BHI broth was examined within 32 days of storage (2,4,8,16,32) considering two level of pH (5.5,6.5), three different salt concentration (0.5,3,6)%, three different temperature (15,25,35) °C and finally usage of nitrite treatment of 80 ppm (or not using that, i.e. control treatment). In the third step toxigenesis was performed according to the USDA instruction and mouse bioassay.The results evaluated with completely randomized ANOVA, in SAS system, version 9.and indicated a significant statistical differences among different concentration of salt, pH, temperature and nitrite within turbidity times (p0.0001) 6% salt, pH:5.5, temperature of 15 °C and sodium nitrite(80ppm) and control treatment within 32 days of storage inhibit growth and toxigenesis of Clostridium botulinum type A with inoculum size level of 4×104 cfu/ml in contrast with salt (0.5,3)%, pH:6.5 and temperature (25,35) °C . In pH 6.5, %3 salt, temperature 25 °C and sodium nitrite treatment had more inhibitory effect in contrast with pH:6.5, 0.5% salt, temperature 35 °C and with control treatment.And finally in growth and toxigenesis of bacteria observed a substitute effect between 0.5% salt and nitrite treatment compared to % 3 salt and control treatment. Key words: Clostridium botulinum type A, Sporogenesis, Turbidity, Time to toxicity, Nitrite, pH, Salt, Temperature