Establishment of a Real-time PCR Assay for Detecting and Classifying Shigella
In order to detect and classify Shigella bacteria rapidly and accurately,the primers and probes were respectively designed according to the genes of invC,rfc,wbgZ and rfpB,and a real-time PCR assay was established to identify Sh. castellani including Sh. flexneri,Sh. sonnei and Sh. dysenteriae,then it was verified by specific test and artificial inoculation test with reference to the results of using the primers and probes designed according to ompA gene. The results showed that the specificity was 100% when all 17 strains of Shigella and 19 non-shigella strains were amplified by the established assay;through PCR assay with enrichment broth,the detection limits of Shigella in pasteurized milk,ice cream,acidophilus milk,cheese,cooked meat,sausage and other instant foods were 1–3 cfu/25 g(mL),and that in raw milk,raw meat and milk powder were≤8 cfu/25 mL,12 cfu/25g and≤12 cfu/25 g,respectively;the suspicious bacterial colonies were isolated and cultivated for real-time PCR assay,it was found that the detection limit of all samples was 1–3 cfu/25 g(mL),which was consistent with the result by traditional cultivation method. In short,the real-time PCR assay was rapid,sensitive and specific,which was appropriate for routine detection and identification of Shigella.