Bacteriological analysis of housefly samples across Dhaka city and its antibiotic susceptibility analysis

Abstract

Houseflies (Musca domestica) act as mechanical vectors for pathogens, facilitating the fomite-mediated spread of bacteria in urban environments. This study evaluated the external bacterial load on houseflies in Dhaka, Bangladesh, and characterized the antibiotic susceptibility profiles of the isolates. Thirty-six housefly specimens were collected from street food stalls, fish markets, and residential areas across the city. Individual flies were washed in phosphate-buffered saline, serially diluted, and cultured on MacConkey, mannitol salt, and cetrimide agars for preliminary isolation. Molecular analysis verified Escherichia coli in 14.7% of samples, Staphylococcus aureus in 10.8%, Klebsiella pneumoniae in 9.3%, and Pseudomonas aeruginosa in 0.5%. Antibiotic susceptibility testing via Kirby–Bauer disk diffusion revealed highest overall sensitivity to meropenem (81.8%), followed by ceftriaxone (70.5%), doxycycline (70.5%), and amikacin (54.5%). Vancomycin exhibited a 62.5% susceptibility rate against S. aureus itself (5 out of 8 isolate) but a 22.7% susceptibility over all isolates, considering both Gram-positive and negative bacteria. In contrast, amoxicillin showed only 4.5% susceptibility and 95.5% resistance. High resistance rates were also noted for cefixime (77.3%) and ciprofloxacin (30.6%) with ceftriaxone showing the least resistance (13.6%). The detection of multidrug-resistant bacteria on housefly surfaces underscores their role in disseminating clinically significant pathogens. These findings highlight the urgent need for improved sanitary measures, vector control strategies, and antibiotic stewardship to mitigate the public health risks posed by synanthropic flies.