Molecular Characterization of Escherichia coli O157:H7 and non-O157 Shiga Toxin Producing E. coli from Retail Meat and Humans

Abstract

A total of 550 meat samples (300 minced beef and 250 chicken meat) marketed in Zagazig City, Sharkia Governorate, Egypt, as well as 150 human stool samples were examined for Shiga toxin producing E. coli. Results revealed that the isolation rates of E. coli O157:H7 versus non-O157 were 1.7% versus 2.3% in minced beef, 0.8% versus 2% in chicken meat and 0.7% versus 2.7% in human stools. Other identified serotypes were including O111:H8 (25%), O26:H11 (20.8%), O55:H7 (16.7%) and O113:H21 (4.2%). Virulence associated genes were identified in E. coli serotypes, stx1 and stx2 were characterized in 16.7% and 62.5% of the isolates, while, eaeA and hlyA genes were identified in 50% and 70.8% of the examined serotypes, respectively. Genotyping of E. coli O157:H7 serotype from different sources using Enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR) fingerprinting revealed heterogenicity of the isolates, however, human and minced beef isolates were grouped in the same cluster indicating potential transmission of infection from contaminated beef to human consumers. In conclusion, ERIC-PCR is a highly discriminatory, reliable and cost-effective tool for tracing sources of infection with bacteria. Public health education and application of strict hygienic measures during slaughtering, transportation and preparation of meat are essential to minimize the risk of contamination and transmission of infection to consumers.

Occurrence of Virulence Genes and Antimicrobial Resistance of E. coli O157:H7 Isolated from the Beef Carcass of Bahir Dar City, Ethiopia

“…PCR verified the presence of the stx2 gene at the expected molecular size of 350 bp in 56% isolates which were more than stx1 (only 32% isolates harbored it). This finding was in agreement with studies in California [ 47 ], China [ 41 ], Egypt [ 42 ], and Modjo, Ethiopia [ 20 ]. The strains carrying stx2 are potentially more virulent than those carrying stx1 or even strains carrying both stx1 and stx2 [ 22 , 42 , 47 ].…”

“…This finding was in agreement with studies in California [ 47 ], China [ 41 ], Egypt [ 42 ], and Modjo, Ethiopia [ 20 ]. The strains carrying stx2 are potentially more virulent than those carrying stx1 or even strains carrying both stx1 and stx2 [ 22 , 42 , 47 ]. On the contrary, 36% of the isolates do not have either of the two Shiga toxin-producing genes.…”

“…The frequency of isolation of E. coli O157:H7 in swab samples taken from the carcass in this study was 8.9%. This result was in agreement with other reports in different countries with 8% in Debre Zeyit and Modjo [ 21 ] and 8.1% in Modjo, Ethiopia [ 12 ], and 9.3% in Jimma [ 40 ], but these data indicated high frequency of occurrence relative to reports from Haramaya University (2.2%) and Dire Dawa slaughterhouses (4%) [ 2 ] and swab samples taken from the carcass in the Hawassa municipal abattoir (2.7%) [ 19 ], Modjo (4.17%) [ 20 ], China (2.7%) [ 41 ], and Egypt (3.1%) [ 42 ]. On the contrary, it was lower than the culture-based prevalence of E. coli isolates (22.2%) from meat samples collected from the Mekelle municipal abattoir in northern Ethiopia [ 43 ].…”

“…The gene was mostly reported in STEC strains associated with severe human illnesses such as bloody diarrhea and HUS. However, STEC strains lacking the eae gene have been reported to cause outbreaks [ 42 , 47 ]. In addition, hlyA is carried on the plasmid, and the bacteria can lose the gene together with the plasmid upon subsequent culturing, and this could be one reason for not detecting hlyA in all the isolates [ 49 ].…”

Characterization of Shiga toxin-producing Escherichia coli isolated from cattle and their contacts

“…Strains of STEC are characterize by production of different virulence genes including shiga toxin (stx1 and stx2) which inhibit the synthesis of host cell protein leading to cell death, beside the adherence factor, intimin, coded by eae gene which play a critical role in intestinal attachment [5]. An additional virulence factors that harbored by some strains of STEC is enterohaemorrhagic hemolysin which encoded by hlyA gene and associated with extra intestinal lesions and seems to affect several cells including erythrocytes, renal cells, lymphocytes and causing severe human illness [7].…”