Isolation and identification of Escherichia coli O157:H7 from houseflies (Musca domestica L) at cattle barns in Al-Qadisiyah Province, Iraq

Recent studies identified that Escherichia coli O157:H7 (ECO157H7) causes hemorrhagic colitis in humans, a rare spectrum of diarrheal illness. According to the findings of epidemiological investigations, cattle serve as the principal reservoirs for this bacterium. This study was conducted to understand the incidence of ECO157H7 in houseflies (HFs), a key disease vector. HFs (n = 40) were collected from cattle barns. The HFs were cultured on MacConkey (MC) agars, and any suspected colonies were grown on Eosin Methylene Blue (EMB) agar. EMB-based metallic sheen colonies were grown on specific media, such as sorbitol Chromagar (SCA) and cefixime tellurite sorbitol-MacConkey (CT–SMAC) agar. Sorbitol non-fermenting (SNF) isolates were subjected to a commercial latex agglutination kit to identify the existence of O157 group. The results recorded 31/40 (77.5%) E. coli isolates identified from HF samples. The findings revealed that only 18/31 (58%) were from the SNF isolates. The identities of the isolates were further examined by targeting the rfbO157 and fliCH7 genes, as genetic markers in a PCR method. The PCR results reported 10/18 (55.5%) and 12/18 (66.6%) isolates that carried the rfbO157 and fliCH7 genes, respectively. Our research revealed that HFs represent a harbor for the pathogenic E. coli. The ecology and way this bacterium spreads among animals and across the environment may depend heavily on the presence of ECO157H7 in agricultural environments.