Characterization of Shiga Toxin-Producing Escherichia coli from Animal Sources Causing Human Infection
Shiga toxin-producing Escherichia coli (STEC) represent a severe public health issue worldwide, causing life-threatening diseases in the human gastrointestinal tract. This study aimed to determine the occurrence of virulent and antibiotic-resistant STEC in retail meat, milk products and human stool samples and to characterize the genes encoding for virulence and antibiotic resistance among the identified STEC isolates. Therefore, a total of 260 food samples (minced meat, beef luncheon, oriental sausage, beef burger and Karish cheese) were collected from retail markets in different localities at El Giza Governorate, Egypt. Additionally, 50 stool specimens were taken from children that had diarrhea at Imbaba Fever Hospital. Bacteriological examination showed a relatively high occurrence of E.coli in meat products (25%), in karish cheese (20%) and in human (28%) specimens. Serotyping of the food product isolates revealed the predominance of non-O157 (82.3 %) with the following serotypes; O26, O27, O53, O71, O95, O103, O111, O124, O125, O127, O145 and O164. Similarly, the diarrheic children stool specimens showed the presence of O71, O95, O111, O127, O55 and O164. The O157serotype was detected only in one food and one human isolates. The overall occurrence of STEC in food products was 35.7%, where stx1 gene was detected in 4 serogrups, while Stx2 was found only in the O103 serotype belongs to minced meat sample. Single presence of eaeA gene was recorded in 3 serogroups belong to minced meat, beef burger & karish cheese, as well as from only one diarrheic children. Antibiotic susceptibility of the examined isolates using disk diffusion test indicated that the highest resistance pattern of food (9 of 14, 64.3%) and human (4 of 4, 100%) isolates was against cephalothin KF30. However, all isolates were sensitive to chloramphenicol, ciprofloxacin, amikacin, and gentamycin. Examination of the resistance gene determinants; blaTEM, Tet (A) and aadA2 demonstrated a high correlation between the phenotype and genotype resistance to cephalothin and tetracycline. DNA sequencing and phylogenetic analysis of the stx2-positive minced meat isolate revealed a high genetic relatedness with beef minced