Molecular Characterization and Antibiogram Profiling of Bacteria Isolated From Sewage and Surface Water in Bangladesh

The global rise of antibiotic-resistant bacteria presents a major threat to public health, complicating the treatment of bacterial infections. This study aimed to identify bacterial pathogens in surface water and sewage samples from the University of Rajshahi, Bangladesh, and evaluate their antibiotic susceptibility. A total of 60 water samples were collected from four distinct locations and analyzed using a combination of culture-based techniques, conventional PCR, and advanced molecular techniques (Sanger sequencing). Eight prevalent bacterial species were identified: <i>Klebsiella pneumoniae</i> (21.6%), <i>Escherichia fergusonii</i> (15%), <i>Enterobacter bugandensis</i> (13.3%), <i>Bacillus paramycoides</i> (8.3%), <i>Comamonas jiangduensis</i> (8.3%), <i>Bacillus albus</i> (6.6%), <i>Klebsiella quasivariicola</i> (5%), and <i>Lysinibacillus xylanilyticus</i> (5%). The 16S rRNA gene sequencing confirmed the identity of the bacterial isolates, and the phylogenetic tree analysis revealed distinct genetic divergence of the Bangladeshi isolates compared to global reference strains. Antibiotic susceptibility against 10 commonly used antibiotics was performed using the Kirby-Bauer disk diffusion method, revealing a varying degree of resistance patterns. All isolated bacteria exhibited susceptibility to imipenem, levofloxacin, amikacin, and azithromycin, while significant resistance was noted against cefradine, amoxicillin/clavulanic acid, cefuroxime, and ceftriaxone. Notably, 44% of the bacterial isolates were identified as multi-drug-resistant (MDR), with <i>K. pneumoniae</i> (69.23%), <i>E. bugandensis</i> (62.5%), and <i>E. fergusonii</i> (55.55%) exhibiting the highest resistance. In contrast, <i>K. quasivariicola</i> and <i>C. jiangduensis</i> exhibited no MDR traits. The multiple antibiotic resistance (MAR) index ranged from 0.30 to 0.60 among the isolates. These findings highlight the significant contamination of water sources with antibiotic-resistant bacteria, underscoring the urgent need for effective management practices to mitigate public health risks.