Incidence and antimicrobial susceptibility pattern of extended-spectrum-β-lactamase-producing Escherichia coli isolated from retail imported mackerel fish

Abstract

During the past few years, extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and other species of Enterobacteriaceae have become a matter of great concern in human and veterinary medicine. Several studies in recent years documented the prevalence and occurrence of ESBLproducing Enterobacteriaceae in food products such as meat, poultry and raw milk; therefore in this pilot study we examined imported raw frozen mackerel fish to determine the incidence of ESBLproducing E. coli from Eastern Province of Saudi Arabia. From January to March, 2012, 45 samples were purchased from various supermarkets of this region and examined for the presence of ESBL-producing E. coli using ChromID ESBL agar plates and further confirmed by PCR amplification. Out of 45 mackerel fish samples, 23 (51.1%) were found to be positive for ESBL-producing E. coli and yielded 60 isolates. The higher rate of resistance was found to be with ampicillin (100%), piperacillin (96.7%), cefotaxime (93.3%), ceftriaxone (93.3%), tetracycline (53.3%), nalidixic acid (40%) and trimethoprim (30%). The least rate of resistance was recorded among chloramphenicol (15%), ciprofloxacin (15%), noroxin (11.7%) and nitrofurantoin (5%). All the 60 isolates in this study were found susceptible to amikacin, aztreonam, cefepime, ertapenem, gentamicin and kanamycin. Further characterization by PCR revealed that 49 (82%) out of 60 isolates of ESBL-producing E. coli were confirmed to be bla_CTX-M type and were negative for bla_TEM and bla_SHV genes. This is the first study to demonstrate the occurrence of ESBL-producing E. coli in imported raw frozen mackerel fish in Saudi Arabia and the study result indicates that the mackerel fish might be the possible reservoir of bla_CTX-M gene and may contribute to the dissemination and transfer of these β-lactamase genes to humans through food chain. The high rate of occurrence of ESBL-producing E. coli in the mackerel fish indicates that there is an established reservoir of these bacteria in the mackerel fish. Further national wide studies are necessary to assess future trends in imported fish to Saudi Arabia.

Key words: Mackerel fish, Escherichia coli, extended-spectrum β-lactamase (ESBL), antimicrobial resistance, PCR.