Background: The housefly Musca domestica and the blowfly Chrysomya megacephala are found worldwide and are medically significant as mechanical vectors of various pathogens from unsanitary locations to food, resulting in diseases in humans.
Objectives: This study aimed to test the antimicrobial activity against Enterococcus spp. isolated from M. domestica and C. megacephala by standard disk diffusion and minimal inhibitory concentration (MIC), and to study the potential of M. domestica and C. megacephala to transfer multi-drug resistant enterococcus to humans.
Material and Method: Seven hundred adult flies were collected from fresh-food markets, garbage piles, restaurants, school cafeterias, and rice paddy fields in Muang Ubon Ratchathani and Warinchamrap in Ubon Ratchathani Province. Antimicrobial susceptibility for Enterococcus spp. isolated from adult flies was performed by disk diffusion test and minimum inhibitory concentration (MIC) determination.
Results: One hundred and twenty isolates of Enterococcus spp. were taken from 67 M. domestica and 53 C. megacephala. Standard disk diffusion showed the Enterococcus spp. isolates exhibited susceptibility to ampilcillin (99.2%), chloramphenicol (74.2%), tetracycline (75.0%), vancomycin (50.8%), and erythromycin (42.5%). The MICs of antimicrobial agents for all isolates were <0.25-8 μg/mL for vancomycin, 1->16 μg/mL for tetracycline, 4->16 μg/mL for chloramphenicol, and 0.5-8 μg/mL for ciprofloxacin.
Conclusion: The study demonstrated the potential of M. domestica and C. megacephala to carry Enterococcus spp. Nine antimicrobial susceptibility patterns were obtained among the 120 enterococci isolates.

Keywords: Enterococcus spp., Musca domestica, Chrysomya megacephala