Critical occurrence of verotox-genic e.Coli and non-typhoidal salmonella in some heat treated dairy products

Abstract

Pathogenic strains of E.coli and Salmonella are common causes of food-borne 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 heat-treated milk products intended for con-sumption in Mansoura university hospitals and hostels, as well as, to investigate their serotypes and virulence potential. Seventy-five 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 contaminat-ed 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 high-ly pathogenic verotoxogenic E.coli (VTEC) and NTS in investigated milk products which could be hazardous for public health and resident in Mansoura hospitals and hos-tels. Hence, the implementation of good hygienic practices together with hazard analysis, and risk-based preventive control measures are rigorously required in the pro-cess of HACCP plan to eliminate the risk of contamination that may occur during the manufacturing process.