Ninety random samples of fresh beef were collected from cattle carcasses slaughtered at 3 different abattoirs at Menoufia governorate (30 of each) in 2018. The sampling site was represented by neck region (chuck) of each carcass. The obtained results revealed the efficacy of five different disinfectants against some food poisoning bacteria including E. coli O26: H11, S. Typhimurium and Klebsiella pneumonia which were isolated and serotyped at abattoir level. In vitro infected samples (3.0×10 6 /cm 2) were examined under the effect of different concentrations of disinfections within contact time 120 minutes. Disinfectant A at concentration 1% was effective against 100% of E. coli O26: H11 and Klebsiella pneumoniae, while concentration 1.5% of disinfectant A was required for elimination of S. Typhimurium, followed by B, C, D and E disinfectants, respectively. On the other hand, D and E disinfectants even in 2% concentration and contact time 120 minutes reduced 99% of the infection.

Ninety random samples (100 gm) of fresh beef were collected from the cattle carcasses slaughtered at 3 different abattoirs in Menoufia Governorate namely A, B and C (30 of each), represented by neck region (chuck) during summer and winter seasons in 2018 (45 samples of each season). The obtained results of serotyping of E. coli revealed that EHEC O26: H11 was the most prevalent among other serogroups 6.67%, 6.67% &13.33% and 6.67%, 13.33% & 6.67%. The prevalence was 46.67% and 40%, 26.67% and 26.67%, and 26.67% and 20.00% for A, B & C abattoirs during the summer and the winter seasons, respectively. Serotyping of salmonella revealed Salmonella Typhimurium was the most prevalent during the summer; 13.33% for each abattoir. The total isolation rate was 33.33%, 26.67% and 20.00% for A, B and C abattoirs, respectively. The most prevalent serogroup during the winter was Salmonella Enteritidis 13.33%, 6.67% and 6.67%, while the total isolation rate was 26.67%, 20.00% and 6.67% for A, B and C abattoirs, respectively. It was concluded that the contamination rate increased in abattoir A than B than C, and the prevalence increased during summer than in winter.