Microbiological Analysis Of Non-Biting Flies Collected From Hospitals: Novel Pathogens And New Vectors In The Clinical Environment

Abstract:
The potential for houseflies Musca domestica to contribute to transfer of the ‘hospital superbug’ Clostridium difficile in hospitals has been demonstrated, highlighting flies as realistic vectors of this microorganism in clinical areas. Subsequent field studies where houseflies were sampled from hospitals have shown carriage of a variety of pathogenic bacteria. This study continues the previous work and reports on the pathogenic bacteria isolated from other non-biting flies in hospitals. Non-biting flies were collected from pre-existing ultra-violet light flytraps located throughout the hospitals. External washings and macerates of fly samples were prepared and inoculated onto a variety of agars and following incubation bacterial colonies identified by biochemical tests. A clinical serotype of Escherichia coli (E1525) was isolated from Calliphora vicina. A non-clinical serotype of E. coli (O71) was isolated from Lucilia sericata. The clinical isolate of E. coli from C. vicina was likely acquired from the hospital environment, so flies should be considered as a route of spread of clinical isolates of bacteria in hospitals. L. sericata likely acquired E. coli O71 from calf faeces then by ingress introduced this non-clinical isolate, novel to the hospital environment. Representing a number of novel findings, various bacterial isolates were recovered for the first time ever from a variety of non-biting flies, including Musca autumnalis, Fannia canicularis, Psychodidae, Phoridae, Sphaeroceridae and Drosophila sp. ‘Drain flies’ / ‘small flies’ are highlighted as an emerging problem or even new vectors in the hospital environment, due to their described carriage of pathogenic microorganisms in the clinical setting.