First Molecular Characterization and Antibiogram of Bacteria Isolated From Dairy Farm Wastewater in Bangladesh

This pioneering study in Bangladesh combines phenotypic and genotypic approaches to characterize antibiotic-resistant bacteria in dairy farm wastewater, addressing a critical gap in regional antimicrobial resistance (AMR) research. Dairy farming is integral to global food production, yet the wastewater generated by these operations is a significant source of environmental and public health concerns, particularly in the context of antibiotic resistance. This study aimed to isolate and identify antibiotic-resistant bacteria from dairy farm wastewater and evaluate their antibiogram profiles to inform effective management strategies. A total of 60 wastewater samples were collected and subjected to conventional bacterial characterization, followed by molecular detection via PCR and 16S rRNA gene sequencing. The study identified <i>Pseudomonas aeruginosa</i> (35%), <i>Escherichia coli</i> (30%), <i>Bacillus subtilis</i> (16.67%), and <i>Acinetobacter junii</i> (8.33%) as the predominant bacterial species. Sequencing results demonstrated high compatibility with reference sequences, confirming the identities of the isolates. Antibiogram analysis revealed significant resistance patterns: <i>P. aeruginosa</i> exhibited the highest resistance to penicillin (85.71%) and amoxicillin (76.19%), while demonstrating greater sensitivity to ciprofloxacin and cotrimoxazole<i>. E. coli</i> showed notable resistance to penicillin (88.89%), amoxicillin, and ceftriaxone, while <i>B. subtilis</i> and <i>A. junii</i> also demonstrated high levels of resistance to multiple antibiotics. Notably, a substantial proportion of the isolates exhibited multidrug resistance (MDR), with MAR indices ranging from 0.37 to 0.75. Moreover, several antibiotic resistance genes (ARGs) including <i>penA</i>, <i>bla</i> _<i>TEM</i> , <i>bla</i> _{<i>CTX</i>-<i>M</i>} , <i>tetA</i>, <i>tetB</i>, <i>tetC</i>, and <i>ermB</i> were detected across the bacterial species, with high prevalence rates in <i>P. aeruginosa</i> and <i>A. junii</i>, suggesting the potential for horizontal gene transfer and further spread of resistance. These findings underscore the critical need for a One Health approach to mitigate the risks posed by antibiotic-resistant bacteria in dairy farm wastewater, emphasizing the critical importance of responsible antibiotic use and sustainable farming practices to protect public health and environmental integrity.