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pR_(ST98) is a large and conjugative resistant plasmid(R plasmid)of 98.6 mega-dalton from multi-drug resistantSalmonella typhi(S.typhi),which was classified to incompatibility group C(Inc C).It has been found that pR_(ST98)made its host bacteria not only antibiotic resistant but also more virulent.In this study we explored the possibilityof plasmid pR_(ST98) in S.typhi carrying the Salmonella plasmid virulence gene-spv.The plasmid pR_(ST98) was isolated,purified and then digested by nine restriction endonucleases to make the plasmid enzyme profile.Spv-specific PCRand Southern blot were applied to identify the virulence gene on pR_(ST98).The amplified spv fragments spvR andspvB were cloned into pGEM-T EASY and then the DNA sequences were analysed.The fragments of pR_(ST98)digested by endonucleases Bgl Ⅱ,Pst Ⅰ and Sac Ⅱ were identified,which may be useful for molecular analysis andfurther epidemiological surveillance of pR_(ST98).The results of PCR and Southern blot showed that spv homologousgenetic sequence which had been found in all pathogenesis Salmonella spp.except S.typhi was also presented onpR_(ST98).The ORF of spvR and spvB of pR_(ST98) were 894 bp and 1,776 bp,respectively.They have more than 99%homology with that of spvR and spvB on virulence plasmid in S.typhmurium.The genotype research on pR_(ST98)revealed that there is a plasmid carrying genes responsible for drug resistance and virulence in S.typhi.This is thefirst report for such kind chimerical plasmid in S.typhi.Cellular & Molecular Immunology.2005;2(2):136-140.
pR_ (ST98) is a large and conjugative resistant plasmid (R plasmid) of 98.6 mega-dalton from multi-drug resistant Salmonella typhi (S. typhi), which was classified to incompatibility group C (Inc C) (ST98) made its host bacteria not only antibiotic resistant but also more virulent.In this study we explored the possibility of plasmid pR_ (ST98) in S. typhi carrying the Salmonella plasmid virulence gene-spv. The plasmid pR_ (ST98) was isolated, purified and then digested by nine restriction endonucleases to make the plasmid enzyme profile. Spv-specific PCR and Southern blot were applied to identify the virulence gene on pR_ (ST98). The amplified spv fragments spvR and spvB were cloned into pGEM-T EASY and then the DNA sequences were analyzed. The fragments of pR_ (ST98) digested by endonucleases Bgl II, Pst I and Sac II were identified, which may be useful for molecular analysis and further epidemiological surveillance of pR_ (ST98). The results of PCR and Southern blot showed that spv homologousgenetic sequence which had been found in all pathogenesis Salmonella spp.except S. typhi was also presented onpR_ (ST98). The ORF of spvR and spvB of pR_ (ST98) were 894 bp and 1,776 bp, respectively. They had more than 99% homology with that of spvR and spvB on virulence plasmid in S. typhmurium. genotype research on pR_ (ST98) revealed that there is a plasmid carrying genes responsible for drug resistance and virulence in S.typhi.This is the first report for such kind chimerical plasmid in S. typhi. Cellular & Molecular Immunology. 2005; 2 (2): 136-140.