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Molecular analysis and identification of virulence gene on pR(ST98) from multi-drug resistant Salmonella typhi
Rui Huang1, Shuyan Wu, Xueguang Zhang
1Department of Microbiology, Medical College of Soochow University, Suzhou 215007, China. hruisdm@163.com
Abstract:
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). It has been found that pRST98 made its host bacteria not only antibiotic resistant but also more virulent. In this study we explored the possibility of plasmid pRST98 in S. typhi carrying the Salmonella plasmid virulence gene - spv. The plasmid pRST98 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 analysed. The fragments of pRST98 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 homologous genetic sequence which had been found in all pathogenesis Salmonella spp. except S. typhi was also presented on pR(ST98). The ORF of spvR and spvB of pRST98 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 the first report for such kind chimerical plasmid in S. typhi.
Insights
A large Salmonella typhi plasmid, pR(ST98), carries virulence genes (spvR and spvB), contributing to antibiotic resistance and increased bacterial pathogenicity. This study identifies a unique chimeric plasmid in S. typhi.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Salmonella typhi (S. typhi) can harbor large, conjugative R plasmids that confer antibiotic resistance.
- The R plasmid pR(ST98) from multi-drug resistant S. typhi has been linked to increased bacterial virulence.
- The presence and role of Salmonella plasmid virulence (spv) genes on R plasmids in S. typhi remain largely unexplored.
Purpose of the Study:
- To investigate if the R plasmid pR(ST98) in S. typhi carries the Salmonella plasmid virulence (spv) gene.
- To characterize the spv genes identified on the pR(ST98) plasmid.
- To determine the implications of this plasmid for S. typhi drug resistance and virulence.
Main Methods:
- Isolation and purification of the R plasmid pR(ST98).
- Restriction endonuclease digestion and analysis of plasmid fragments.
- Spv-specific PCR and Southern blot hybridization to detect virulence genes.
- Cloning and DNA sequencing of amplified spvR and spvB fragments.
Main Results:
- The R plasmid pR(ST98) was successfully isolated and its enzyme profile determined using nine restriction endonucleases.
- PCR and Southern blot confirmed the presence of spv homologous sequences on pR(ST98).
- The open reading frames (ORFs) for spvR (894 bp) and spvB (1,776 bp) were identified with >99% homology to those in S. typhimurium.
Conclusions:
- The R plasmid pR(ST98) in S. typhi harbors both antibiotic resistance genes and the Salmonella plasmid virulence (spv) genes.
- This represents the first report of such a chimeric plasmid in S. typhi, combining drug resistance and virulence factors.
- The findings provide insights into the molecular mechanisms of S. typhi pathogenesis and offer targets for epidemiological surveillance.
