Molecular tracing of infection source of rare H₂S negative strains of Salmonella Senftenberg

Objective To investigate the genetic clone characteristics of rare H₂S negative strains of Salmonella enterica subsp.enterica serovar Senftenberg (S.Senftenberg).Methods A retrospective analysis was performed to explore the characteristics of biochemical test, encoding Salmonella pathogenecity island gene 1 (SPI-1) and antibiotic resistance of S.Senftenberg from diarrhea patients in Shanghai Global Salm-Surv (GSS).Ribotyping comparisons were made between typical and atypical strains of S.Senftenberg using Riboprinter^® (RP) DNA finger printing technique.Using cluster analysis we compared the molecular subtyping of these strains with the same serotyping strains in China PulseNet dynamic database by PFGE.Results Of 19 strains of S.Senftenberg isolated from Changning district GSS-Surv hospital, there were 10 phenotype variant strains found to be H2S negative and lacking SPI-1.There were two different clones between variant strains and typical strains, which was proved by RP Ribotyping.Thirty six strains of S.Senftenberg including 19 strains from Changning district were divided into 18 PFGE typing-pattens by China PulseNet database.The PFGE subtype 4 (2 strains) and 6 (6 strains) were the predominant epidemic strains of variant strains, the subtype 11 (1 strains), 17 (4 strains) and 23 (2 strains) were the predominant epidemic strains of typical strains in Changning district.Cluster analysis showed the clone of variant strains was higher than that of the typical strains in genetic similarity.Conclusion The molecular tracing of source confirms that variant strains of S.Senftenberg lacking SPI-1 can induce sporadic outbreak as the typical strains.There was homologous nature between H₂S negative variant strains of S.Senftenberg isolated from diarrhea patients in 2006 in Changning district and two strains of S.Senftenberg lacking SPI-1 from a food-borne disease outbreak in 2002 in Shenzhen.