Molecular characterization of biofilm producing Escherichia coli isolated from beef value chain in Bangladesh

Escherichia coli is a notorious ubiquitous organism among the foodborne pathogens which can form biofilm leading to the development of antibiotic resistance. We aimed to investigate E. coli isolated from a total of 240 raw beef and ready-to-eat samples obtained from the capital of Bangladesh along with the microbial quality of the samples. The isolates underwent antibiogram profiling in accordance with the Clinical and Laboratory Standards Institute Guideline 2023 and characterized for the presence of antibiotic resistance genes, as well as for phenotypic and genotypic detection of biofilm formation. The average total aerobic counts and specific bacterial counts exceeded the recommended limit by Bangladesh Food Safety Authority. Among the samples, 86 (36%) samples were positive for E. coli. The antibiogram profile depicted diverse resistance patterns with the highest resistance to ampicillin (100%), amoxicillin (81%), ciprofloxacin (71%), and azithromycin (67%). However, vancomycin (64%), meropenem (57%) and aztreonam (51%) were the most sensitive antibiotics to the isolates. The antimicrobial resistance encoding genes bla_TEM (72%) and tetA (65%) were the most prevalent where the percentage of bla_OXA-1, bla_CITM, bla_NDM-1, bla_CTX-M-2, bla_CTX-M, bla_CMY, bla_CTX-M-1 and bla_SHV genes were 42%, 33%, 6%, 20%, 17%, 16%, 14% and 9% respectively. Phenotypic characterization, utilizing Congo red agar and microtiter plate tests, identified 53 out of 86 isolates as biofilm producers, with 10 classified as strong producers, and 8 and 35 as intermediate and weak producers, respectively. Molecular detection methods revealed that among the 53 isolates positive for biofilm production, 96% carried the csgA gene. Additionally, high prevalence rates were observed for fliC (80%), bcsA (66%), and fimH (60%), indicating their significant roles in biofilm formation. Conversely, the prevalence of agn43 was lower, with only 30% of isolates harboring this gene. This study addresses a knowledge gap, highlighting the public health risks associated with biofilm-producing foodborne pathogens and the emergence of antimicrobial resistance, underscoring the necessity for improved hygiene practices to mitigate the public health threats posed by these pathogens.