Identification and Molecular Characterization of Escherichia coli O157:H7 Isolated from Some Iraqi Patients in Baghdad City

Abstract

Escherichia coli O157:H7 is known to cause illness in animals and people. Their main criterion is to produce a potent toxin that causes damage to the intestine leading to bloody diarrhea. Outbreaks are caused by contaminated food, this strain is the prevalent one, and in severe cases, it may cause death. Forty fecal samples were collected around Baghdad from patients residing in Yarmouk and Al-Kindy Teaching Hospitals with typical symptoms of infection with E. coli. All 40 fecal samples (15 male, 15 female, and 10 children) were the source of the bacterium and were immediately transported to the laboratory and cultured for further processing. Among 40 samples collected from humans, only 20 were identified as E. coli O156:H7. Further confirmation was made by culturing on MacConkey agar, Eosin Methylene Blue (EMB) agar, to assess the development of a metallic sheen. Final bacteriological confirmation came after cultivation on HiCrome™ EC O157:H7 Selective Agar Base, modified with supplement (FD187) that gave dark purple to magenta coloration for these strains of bacteria. Molecular identification of isolated strains came from investigating two specific genes through PCR amplification, stx1, and rpoB. Both genes were amplified, sequenced, and registered in NCB with accession no. OR939814 and PP059841, respectively. Bacterial isolates studied in this research were classified to the species level and found to be STEC Escherichia coli O157:H7 Sakai strain. This study aimed to identify the epidemic strain of E. coli through a highly accurate approach by sequencing the rpoB gene, and identifying the type of Shiga toxin produced by this bacterium.