Prevalence and characterization of Shiga toxin O157 and non-O157 enterohemorrhagic Escherichia coli isolated from different sources in Ismailia, Egypt

Shiga toxin producing Escherichia coli (STEC) is recognized as important food borne pathogen, responsible for sporadic cases of serious outbreaks worldwide. The morbidity and mortality associated with several recent outbreaks due to STEC have highlighted the threat this organism poses to public health. This study was conducted to identify and characterize the virulence traits and antibiotic resistance of enterohaemorrhagic E. colifrom different sources, between September 2008 and October 2009. A total of 384 samples from human, animal and environmental sources were collected from different locations in Ismailia, Egypt. E. coli isolates (n = 283) were identified by conventional microbiology culture and were phenotypically characterized using biochemical and motility tests. Multiplex PCR (mPCR) was applied for the detection of virulence genes (stx1, stx2,eaeA and EHEC hlyA). From the overall number of E. coli isolates, 31.4% (89/283) were isolated from stools of humans with diarrhea, 17.3% (49/283) from stools of sheep, cattle and chicken with diarrhea, 16.6% (47/283) from urine of humans with urinary tract infection, 17.3% (49/283) from water, 6.4% (18/283) from sea-food, 6% (17/283) from processed meat products, 3.9% (11/283) from dairy products and 1.1% (3/283) from poultry products (liver). The antibiotic resistance patterns showed that the isolates carried multi-drug resistance (MDR) phenotype to at least four antibiotics belonging to different classes: Erythromycin (E), gentamicin (CN), cefazolin (CZ), thiampinicol (TP), vancomycin (VA), ciprofloxacin (CIP) and ampicillin (AM). Shiga toxin genes were identified in 10 (3.5%) suspected Enterohaemorrhagic E. coli isolates by mPCR. Serotyping of these 10 isolates demonstrated five different serogroups (O157, O158, O114, O125 and O26): three human isolates (serogroups O157, O158), four animal isolates (serogroups O114, O26), two isolates from meat products (serogroups O125, O158) and one isolate from water (serogroup O114). This study identified STEC O157 from human cases with diarrhea, and demonstrated that meats and water could be contaminated with more than one STEC serotype. This is a concern due to their potential to cause human infections.   Key words: Hemorrhagic Escherichia coli, Shiga toxin, non-O157, O157, diarrhea, food, Egypt