Determination of Virulence Factors and Antibiotic Resistance Profile of E. coli O157:H7 in some Marine and Freshwater Fish from Samsun, Türkiye

In this study, Escherichia coli O157:H7 contamination was investigated in Engraulis encrasicolus, Merlangius euxmus, Trachurus mediterraneus, Mullus barbutus, Tinca tinca, Cyprinus carpio and Oncorchynhus mykiss (total of 300 samples). The presence of certain virulence genes such as shiga toxin 1 (stx1), shiga toxin 2 (stx2), intimin (eaeA), and hemolysin (hlyA) was determined. The E-test method was employed to determine the antibiotic resistance profile and minimum inhibitory concentration (MIC) values of the isolates. Out of a total 141 freshwater fish samples, E. coli O157:H7 was detected in 5 of them (3.5%). In 159 marine fish, 2 of them (1.25%) were E. coli O157 positive. In terms of virulence characteristics, the E. coli O157:H7 isolate obtained from the Oncorhynchus mykiss sample had the stx1, eaeA, and hlyA genes. Both eaeA and hlyA genes were determined as positive in the E. coli O157 isolate identified from the Merlangius euxmus sample. Resistance to tetracycline, cefotaxime, cefepime, ciprofloxacin, gentamicin, ertapenem and cefoxitin was demonstrated in both samples. In this study, the presence of E. coli O157 in fish, detection of virulence genes and antibiotic resistance profile indicate the potential risk of infection from contaminated seafood.