STEC non-0157 strains in meat from Southern Sonora, Mexico and their antibiotic resistance

Escherichia coli is one of the most important bacteria associated with the consumption of meat products causing human disease, with bovines as the main reservoir for this organism. Escherichia coli serogroups producing the Shiga toxin (referred as STEC) include both O157:H7 and non-O157 strains can cause Hemolytic Uremic Syndrome (HUS). STEC have been previously founded in raw meat sampled at slaughterhouses. The goals of this study were 1) to detect STEC O157 and non-O157 strains in meat cuts and products (beef and pork) in TIF and non-TIF slaughterhouses, as well as butcheries, in southern Sonora, Mexico, and 2) to verify the antibiotic resistance/susceptibility pattern of E. coli strains, which contain any toxin-producing gene. To achieve the first aim, two selective media (TS-SMAC agar and Rainbow ® agar O157) were employed to obtain putative O157:H7 colonies, followed by multiplex PCR for the stx 1, stx 2, eaeA , and rfB genes, using the O157:H7 serotype as a control. No STEC O157 was found in the beef products, but some non-O157 isolates were found. These isolates contained the stx 2 pathogenicity gene (1.40 %, 3/224) and/or the fliC H4 flagellar antigen (1.78 %, 4/224). This work also confirmed the susceptibility/resistance of strains with the stx 2 and/or fliC H4 genes to several antibiotics and multi-resistance of all or some of these strains to trimethoprim/sulfamethoxazole, tetracycline, clarithromycin, penicillin G, oxacillin, ampicillin, and cefazolin.