Critical occurrence of verotoxgenic E.coli and non-typhoidal salmonella in some heat treated dairy products

Abstract

Pathogenic strains of E.coli and Salmonella are common causes of foodborne illness and have been frequently isolated from inadequately heat-treated milk products in Mansoura city. The current study was performed to explore the prevalence of E.coli and Salmonella spp. in heattreated milk products intended for consumption in Mansoura university hospitals and hostels, as well as, to investigate their serotypes and virulence potential. Seventyfive samples of heat-treated milk products (Soft cheese, yoghurt, and processed cheese, 25 of each) were randomly gathered and directed to further investigation using conventional and molecular microbiology. Result revealed that 3(12%) of soft cheese samples harbored E.coli O146:H21, O26:H11 and O128:H2 serotypes and 2(8%) of yoghurt samples were contaminated with O128:H2 and O121:H7 serotypes while 3(12%) of processed cheese samples were positive for non-typhoidal Salmonella (NTS) serovars (Salmonella Typhimurium, Salmonella Infantis and Salmonella Essen). Virulence gene profiling reported that all E.coli isolates harbored eaeA gene and only E.coli O26:H11 and O121:H7 encoded stx2 (verotoxin) gene. Further, all Salmonella isolates harbored invA and stn genes, while only Salmonella Typhimurium and Salmonella Infantis encoded spvC gene. This study confirmed the existence of highly pathogenic verotoxogenic E.coli (VTEC) and NTS in investigated milk products which could be hazardous for public health and resident in Mansoura hospitals and hostels. Hence, the implementation of good hygienic practices together with hazard analysis, and risk-based preventive control measures are rigorously required in the process of HACCP plan to eliminate the risk of contamination that may occur during the manufacturing process.