Comparative Study of 2 Quantitative Methods for Salmonella Count in Fresh Meat Specimens

Objective To find an accurate, practical,precise and selective counting method of Salmonella in fresh meat specimen and provide scientific basis of microbial risk assessment. Methods Diluting the samples that polluted with different numbers of Salmonella species, the plate count method and MPN method were adopted to count the value,made comparison of these two methods on accuracy, sensitivity and practicability. Choose CHROMagar Salmonella plate and XLD agar plate as separating plate in plate count method, the total number of definite Salmonella clones on each plate was counted after identifying the suspected colonies. At the same time,select the TTB,MM and SC enriched broth to culture the polluted sample at 36±1 ℃ and 42±1 ℃ in MPN method respectively,inoculate the enriched broth to GHROMagar Salmonella plate and XLD agar plate,and the total number of definite Salmonella within 1 cfu/g to 500 cfu/g in plate count method. Results The culture effect of SC enrichment broth was the best at 42±1 ℃ in MPN method,its lowest detection limit was 10cfu/g and the coincidence rate of the examination value and theory value (500cfu/g) was 92.0% Conclusion The MPN method is better than the plate counting method both in sensitivity and applicability.