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)

ABSTRACT

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.