Distribution in different Salmonella serovars and integration sites of Salmonella para-typhi C phage SPC-P1 / 北京大学学报(医学版)

Objective:To determine the prevalence of Salmonella paratyphi C phage ( SPC-P1 ) in dif-ferent Salmonella serovars and to identify the integration sites in host genome. Methods: Based on the complete genome of SPC-P1 in S. paratyphi C RKS4594, 6 pairs of primers were designed and used to amplify the fragments of SPC-P1 in 11 S. typhi, 11 S. paratyphi A, 12 S. paratyphi B and 23 S. para-typhi C strains. At the same time, 100 complete genomes of Salmonella including 20 serovars available in National Center for Biotechnology Information ( NCBI) database were downloaded and aligned by Mauve 2. 3. 1 to determine the prevalence of SPC-P1 in these serovars. Primers were designed according to the integration sites of SPC-P1 in the genome of RKS4594 , and used to amplify ten strains having SPC-P1 in the genome. The PCR products were sequenced to investigate the integration sites of SPC-P1. Results:SPC-P1 was widely distributed in S. paratyphi C genome. In the study, 14 strains had all 6 fragments and 2 strains had 3-5 fragments. All the amplified fragments showed expected sizes. In contrast, in the ge-nomes of S. typhi, S. paratyphi A and S. paratyphi B, no or only 1-2 fragments could be amplified, and the sizes were smaller than expected. The results from Mauve showed that only in the genome of S. choleraesuis, which was a close relative of S. paratyphi C, there existed an almost complete genome of SPC-P1. The insertion site of SPC-P1 in all the ten S. paratyphi C strains tested was between pgtE and yfdC genes. Conclusion:SPC-P1 is a unique virulence factor of S. paratyphi C. It may play roles in the host range and pathogenicity of S. paratyphi C.

Sequencing of Flic genes of Salmonella typhi, S. paratyphi A, S. paratyphi B, S. paratyphi C, and S. typhimurium and application for PCR to differentiate them

All Flic genes of Salmonella typhi, S. paratyphi A, S. paratyphi B, S. paratyphi C, and S. typhimurium code for phase 1 of H antigen (H:1) (d, a, b, c and i antigen respectively). The genes were sequenced on Sanger's principle by automatic sequenser (ABI, 3100 Avant, Genetic Analyser). The primer pairs for the Salmonella species were designed on the basis of the collected sequences. The results showed that PCR with these primers can clearly differentiate the five Salmonella strains, especially between S. paratyphi B and S. typhimurium.