Prevalence and characterization of Shiga toxin-producing Escherichia coli (STEC) in fruits and vegetables sold at local street markets in Alexandria, Egypt

Abstract

This is the first report on the prevalence of Shiga toxin-producing Escherichia coli strains (STECs) in fresh produce sold at local street markets in Alexandria. A total of 945 samples were enumerated for total aerobic mesophilic bacteria (AMC) and E. coli (ECC). AMC ranged from <0.69–5.92 and <0.56–4.98 Log10 CFU g−1 in fruits and vegetables respectively. High flavonoid contents and anti-oxidant capacity inhibited E. coli growth in some types. 80% of samples were contaminated with E. coli, and 4.23% were tested E. coli O157:H7 positive biochemically and serologically. Multiplex PCR detected STEC O157:H7 in 20% (2.3%) of produce types, with virulence markers: stx2; 59% (13/22), stx1; 54.5% (12/22), eaeA; 45.45% (10/22), and hlyA; 18.18% (4/22). The most prevalent toxin genotype was that of STECs possessing stx1-eaeA (27.3%), stx2-eaeA (22.7%), and stx1-stx2 (13.6%). Multidrug resistance was observed in 86.4% of the STECs, 46.4% of which were stx2-positive. Resistance of eaeA-positive STECs to fluoroquinolones constitute health threat to consumers, where resistance determinants can spread among non-pathogenic bacteria in the gastrointestinal tract due to plasmid mobility. Findings of this research call for immediate actions by the Egyptian Food Safety Agency to ensure constant supply of safer produce to local markets nationwide.