Increasing prevalence of hydrogen sulfide negative Salmonella in retail meats

Hydrogen sulfide (H₂S) production is considered a typical characteristic of Salmonella and an important marker for Salmonella isolation. In this study, a total of 82 (26%) Salmonella strains were isolated from 113 chicken and 204 pork samples, within which 49 Salmonella strains were H₂S positive and 33 were H₂S negative. Salmonella enterica serovar Derby was most prevalent in both pork and chicken followed by S. Typhimurium in pork and S. Heidelberg in chicken. Salmonella isolated from pork exhibited a much higher H₂S positive rate than those from chicken (68% versus 31%). The most prevalent H₂S negative serotypes were S. Derby (40%) and S. Heidelberg (30%) in chicken, and S. Typhimurium (23%) and S. Enteritidis (23%) in pork. spvC, a plasmid-encoded virulence marker, was detected in 51% and 42% of the H₂S positive and negative Salmonella respectively. The presence of the two most important serotypes, S. Enteritidis and S. Typhimurium, as well as a virulence plasmid in H₂S negative Salmonella suggested that H₂S negative Salmonella is also a significant public health concern. Such finding warrants the development of an improved method for effective coverage of H₂S negative Salmonella.