Research and characterization of Escherichia coli O157 strains isolated from ovine carcasses of two slaughterhouses of Algiers city

by the stx1 and stx2 genes, which are responsible of the death of intestinal, vascular and renal cells (Fegan & Desmarchelier 1999). The epidemics identified to date are mainly related to the consumption of food of bovine origin, but the ingestion of other foodstuffs and/or water, in direct contact with animals and fecal-oral human-to-human transmission are also implicated (Caprioli et al 2005). Three breeding types are distinguished in Algeria: the bovine, the ovine-caprine, and the poultry. The ovine population predominates and accounts for up to 70% of the total population with more than 12 million sheep. In North Africa and particularly in Algeria, the sheep portability of STEC is not well known yet. Since these germs are not systematically sought even in hospitals, their involvement as pathogens may go unnoticed. This study aims to assess the contamination level of ovine meat obtained in two slaughterhouses in Algiers by the E. coli O157. For this, we first sought the presence of these strains on the surface of the ovine carcasses and tried to confirm their virulence by the identification of the present genes. Introduction Since their first discovery, Escherichia coli O157: H7 strains and other enterohemorrhagic E. coli (EHEC) are known to be the main infectious agents responsible for hemorrhagic diarrhea, their main reservoir being represented by ruminants (Riley et al 1983). These E. coli produce one or more Shiga-toxins (Stx), and that’s why they are called Shiga toxin E. coli (STEC) (Griffin & Tauxe 1991; Seibt et al 1997). Since 1982, EHEC, particularly those of O157: H7 serotype, have often been implicated in Hemorrhagic colitis epidemics (Caprioli et al 2005). 5 to 10% of infected people, particularly young children and the elderly, develop severe complications, such as the hemolytic and uremic Syndrome (HUS) (Griffin & Tauxe 1991; Seibt et al 1997). EHECs have an arsenal of virulence factors whose exact list and roles are yet to be determined. The two major proteins involved in their pathogenicity are, on the one hand, the intimin, encoded by the eae gene and responsible for specific lesions of the enterocytes known as “attaching-effacing lesions (A/E)” and diarrhea, and, on the other hand, the Shiga-toxins, encoded Abstract. Objective: This study aims to identify and characterize Escherichia coli O157 strains isolated from ovine carcasses of two slaughterhouses of Algiers city. Material and method: One hundred and fifty-one (151) parts of sheep carcasses were swabbed by a non-destructive method based on double swabbing process (wet/dry) at two slaughterhouses of Algiers city for the identification and investigation of E. coli O157 strains. The E. coli O157: H7 isolation required a non-selective enrichment step followed by one of immuno-concentration of the bacteria throughout the immunomagnetic separation (IMS) technique and another one for bacteria isolation (on CT-SMAC agar Cefixime Tellurite Sorbitol–MacConkey). The presence of O157 somatic antigen and H7 flagellar antigen in the isolated suspicious doubtful colonies was confirmed by the anti-O157 latex and H7 antiserum agglutination assays. Confirmation of the virulence of the isolated E. coli O157: H7 strain was obtained performed by gene amplification (PCR – Polymerase Chain Reaction). Results: The presence of E. coli O157: H7 was shown in eleven ovine carcasses out of the 151 tested with a prevalence rate of 7.26%. Nine of these carcasses came from the first slaughterhouse and two of them from the second one. Amongst the eleven positive carcasses, thirteen strains of E. coli O157: H7 were isolated: ten strains are sorbitol and β-glucuronidase-negative, and three of them are sorbitol and β-glucuronidase-positive. Among them, seven strains (53.85%) showed an eae stx2 pathotype, one strain (7.69%) showed eae stx1 pathotype, one strain (7.69%) showed the eae pathotype, and three strains (23.08%) showed stx2 pathotype. Only one strain (7.69%) had no gene encoding the virulence factors. Conclusion: The obtained results revealed that sheep are carriers of E. coli O157: H7 in Algeria. Appropriate hygiene and control measures at the slaughterhouse level must be implemented to provide a safe product for the consumer.