EPIDEMIOLOGY AND MOLECULAR CHARACTERIZATION OF MULTIDRUG RESISTANT ESCHERICHIA COLI ISOLATED FROM FISH

Abstract

Antimicrobial Resistance (AMR) has become an alarming global concern due to the widespread dissemination of multi-drug resistant (MDR) bacteria. These bacteria pose a serious threat as they cause infections that are increasingly challenging to treat with existing antibiotics. The surge in the use of antimicrobial compounds across human, animal, and agricultural sectors, coupled with their subsequent release into the environment, has contributed to the emergence of MDR bacteria as a natural bacterial phenomenon. To investigate the prevalence of MDR Escherichia coli (E. coli) in commercial fish samples in Chattogram, a cross-sectional study was designed. Over a six month period from March to August 2022, field sampling was conducted at ten randomly selected prominent fish markets in the Chattogram District. A total of 450 fish samples, including commercial fish, shrimp, and seafood, were purchased from randomly selected vendors. Various methods were employed to analyze the samples, including bacteriological culture-based techniques and the disc diffusion method following the Clinical and Laboratory Standard Institute (CLSI) guidelines. Additionally, uniplex, duplex, and multiplex Polymerase Chain Reaction (PCR) tests were used to determine the occurrence of resistance genes in E. coli isolates. The antibiotic sensitivity profiles of all identified isolates were established against a panel of 20 selected antibiotics belonging to 11 classes. Isolates that exhibited phenotypical resistance against at least 1 agent in 3 or more antimicrobial categories were classified as MDR. The study revealed an overall prevalence of E. coli in fish samples of 41.78% (188/450), with 38.67% prevalence in total study fish samples (174/450). Notably, 92.55% of total fish E. coli isolates (174 out of 188) were identified as multidrug resistant (MDR), exhibiting resistance against antibiotics from multiple categories. The highest resistance was observed against ampicillin, cefalexin, cephalothin, tetracycline, and trimethoprim-sulfamethoxazole. The Multiple Antibiotic Resistance Index (MARI) ranged from 0.15 to 1.00, with an average of 0.50. Of the MDR isolates, 89.36% (168 out of 174) exceeded the maximum MARI value benchmarked at 0.2 or above. The highest MARI value was observed in one MDR E. coli isolate from catfish. The MARI values indicated that the isolates originated from environments with a high-risk source of contamination and significant antimicrobial exposure. Molecular characterization via the Polymerase Chain Reaction uncovered various β-lactam encoding genes, ESBLs, pAmpC, and other non-β-lactam encoding genes of the phenotypically resistant isolates. Among isolates antibiotic resistant genotype prevalence is 83.51% (157/188) and no gene was traced in 16.49% isolates (31/188). xvi | P a g e Among antibiotic resistance gene prevalence of non-β-lactam encoding gene tet-A is highest 85.83%, following sul-2 is 70.09%. Merely, blaTEMis most prevailing among all β-lactam encoding gene with a prevalence of 63.53% following the prevalence of co existence of the bla OXA-1 like gene& blaOXA-2 like gene is 52.38 % detected as ESBLs. Though, no amplification of tet-C and blaACC-1was detected. Genotypic resistance patterns revealed the co-existence of resistance genes of β-lactam encoding genes, PampC, ESBLs, non-β-lactam encoding genes in same or altered fish E. coli isolates. Maximum antibiotic resistant patterns observed were unique. Highest seven resistance gene including blaTEM, PampC, blaCTX, blaCMY-2 like gene, blaCMY-2 like gene, tet-D, sul-2 was noticedin one isolate following six resistance genes was detected in six isolates. Genotypic resistance patterns were observed most frequently in shrimp and commercial fish rather than seafoods. The research's conclusions underscore the significance of fish as sources of MDR E. coli and resistance genes. The data generated could inform the development of mitigation strategies based on public health ethics to avert the emergence of MDR E. coli, addressing the global One-Health challenge posed by this alarming issue.