Detection of mechanically transmitted bacteria by Musca domestica (Diptera: Muscidae) in Malabe Medical Officer of Health (MOH) Division, Sri Lanka

House flies (Musca domestica) have been identified as a mechanical vector, transmitting a range of infectious diseases, including cholera, shigellosis, salmonellosis, and skin infections. They live closely with human and domestic animals and are frequently found in areas of human activities. The present study was conducted to identify the pathogenic microbes potentially transmitted by houseflies since the related knowledge is not available in Sri Lankan settings. Houseflies were collected from the Malabe Medical Officer of Health (MOH) area from September - December 2022 using a prepared bait trap. Collected houseflies were identified up to the species level using standard identification keys. They were sacrificed using a cold shock and were washed in microcentrifuge tubes to collect the bacteria on their outer surface, in 250 µL sterile PBS. A dilution series (10⁰- 10^-7) was made from the original wash, and 200 µL from each dilution was plated on Plate Count Agar and pure cultures for each microbe were obtained. The isolated microbes were identified by performing Gram’s staining and biochemical tests. Acinetobacter spp., Enterococcus spp., Serratia spp., Klebsiella spp., Staphylococcus spp., Pseudomonas spp. and Escherichia spp. were identified and presumed as mechanically transmitted bacteria from houseflies. The most abundant bacterium was Staphylococcus sp. 2  (36.303%), followed by Escherichia sp. (21.452%) and Pseudomonas sp. (17.162%), while other bacteria were present in fewer proportions. The identified genera of the bacteria include some potential pathogenic bacterial species, which could cause mild to severe illnesses. Hence, the findings of the present study emphasized the importance of control measures for houseflies and community awareness programs to reduce the transmission of pathogenic bacteria.