[Prevalence and characterization of Salmonella spp. from foods in South China].

OBJECTIVE

In this study, we studied systematically the prevalence of Salmonella in foods from various parts of South China. Isolated strains were characterized by serotyping and enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR), to provide data support for effectively tracing the source of Salmonella and controlling food contamination.

METHODS

In total 400 unique food samples were collected from retail markets in South China, including meat product (74), frozen product (56), seafood (80), mushroom (54), ready-to-eat food (80), vegetables (32), dairy (24). Food samples were examined by qualitative method according to national food safety standard (GB4789.4-2010) and most probable number (MPN) method. The predominant serotype of Salmonella was figured out when all isolated strains were characterized by serotyping using slide agglutination method. We also applied ERIC-PCR for genetic diversity analysis of Salmonella isolates.

RESULTS

Of the total 400 food samples, 75 (18.8%) tested positive for Salmonella. The results showed that MPN value of 97.3% (73/75) positive samples below 10 MPN/g. Ninety-three Salmonella isolates were belonged to 9 groups and 29 different serovars. Salmonella Derby and Salmonella Typhimurium were the two predominant serovars. The isolated strains were further discriminated by ERIC-PCR. The results revealed 96 strains including 93 isolates, Salmonella Enteritidis CMCC 50335, Salmonella Typhi CMCC 50098 and S. Typhimurium ATCC 14028 were divided into 15 clustering groups and generated 56 genotypes according to the similarity coefficient of 0.75, which suggested various genotypes of Salmonella.

CONCLUSION

The overall prevalence of Salmonella was high, however lower contamination level in foods from cities of South China. S. derby and S. typhimurium were found to be predominant serovars. ERIC-PCR fingerprints database of Salmonella from food samples in South China were preliminarily established. Salmonella present in foods were phenotypically and genotypically diverse.