Antimicrobial resistant and enteropathogenic bacteria in 'filth flies': a cross-sectional study from Nigeria

'Filth flies' facilitate the dispersal of pathogens between animals and humans. The objective was to study the intestinal colonization with antimicrobial resistant and enteropathogenic bacteria in 'filth flies' from Nigeria. Flies from Southern Nigeria were screened for extended-spectrum β-lactamase producing Enterobacterales (ESBL-E), Staphylococcus aureus, Salmonella sp., Shigella sp., Campylobacter sp. and Yersinia enterocolitica by culture. ESBL-E were tested for bla_SHV, bla_CTX-M and bla_TEM; S. aureus was screened for enterotoxins. Spa typing and multilocus sequence typing (MLST) was done for S. aureus and MLST for Escherichia coli. Of 2,000 flies, 400 were randomly collected for species identification. The most common species were Musca domestica (44.8%, 179/400), Chrysomya putoria (21.6%, 85/400) and Musca sorbens (18.8%, 75/400). Flies were colonized with S. aureus (13.8%, 275/2,000) and ESBL-E (0.8%, 16/2,000). No other enteropathogenic bacteria were detected. The enterotoxin sei was most common (26%, 70/275) in S. aureus, followed by sea (12%, n = 32/275). Four S. aureus isolates were methicillin resistant (mecA positive, t674 and t5305, ST15). The bla_CTX-M (n = 16) was the most prevalent ESBL subtype, followed by bla_TEM (n = 8). 'Filth flies' can carry antimicrobial resistant bacteria in Nigeria. Enterotoxin-positive S. aureus might be the main reason for food poisoning by 'filth flies' in the study area.