MOLECULAR CHARACTERIZATION AND VIRULENCE GENES PROFILING OF SHIGA TOXIGENIC E. COLI AND BACILLUS CEREUS SENSU LATO ISOLATED FROM RAW MILK AND SOME DAIRY PRODUCTS

ABOUL EZZ, REEM A. A; ELESAWY, HAMDY A. A; DARWISH, SAMAH F; TAHER, EMAN M

doi:10.21608/avmj.2025.336549.1472

MOLECULAR CHARACTERIZATION AND VIRULENCE GENES PROFILING OF SHIGA TOXIGENIC E. COLI AND BACILLUS CEREUS SENSU LATO ISOLATED FROM RAW MILK AND SOME DAIRY PRODUCTS

Document Type : Research article

Authors

¹ Department of Food Hygiene and Control, Faculty of Veterinary Medicine, Cairo University, Giza, 12211, Egypt.

² Biotechnology Research Unit, Animal Reproduction Research Institute (ARRI), Agricultural Research Center (ARC), Giza, 12556, Egypt

10.21608/avmj.2025.336549.1472

Abstract

Shiga toxin-producing Escherichia coli (STEC) and Bacillus cereus sensu lato have been recognized as major foodborne pathogens that not only poses a significant risk to human health but also result in economic losses in dairy sectors. Therefore, this study was conducted to assess the presence of STEC and B. cereus s.l. in 90 samples of raw milk, baladi yoghurt and white soft cheese (Tallaga) (30 each) according to biochemical identification and molecular characterization of their virulence and toxigenic genes. The obtained results revealed that STEC was detected in 10% of the baladi yoghurt and 6.6% of Tallaga samples, but in contrast, it was not detected in any of the raw milk samples. Meanwhile, B. cereus s.l. was prevalent in 26.6% of the raw milk and 30% of both baladi yoghurt and Tallaga samples. The molecular characterization of toxigenic genes revealed that 80 % of the identified STEC isolates harboured stx_2d_,while only 20% carriedstx_2e; nonetheless, the virulence hlyA and fliCH7 genes were prevalent in 40 & 60% of isolates, respectively. Noteworthy, stx₁, stx_2f, stx₂, stx_2cand eae genes were not detected. B. cereus s.l. isolates, were found to possess toxigenic genes, such as bceT by 96.1% and both of nhe, and cytK by 76.9%. These findings indicated that raw milk and dairy products may be a potential source of STEC and B. cereus as foodborne pathogens as well as, their virulence and toxigenic genes, necessitating strict hygiene measures, along with periodic authority inspections in Egypt’s dairy sector.

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