Housefly (Musca domestica) as Carrier of Enterotoxigenic Staphylococcus aureus in Broiler Farms in Iran: Is it Important for Public Health?

During the last decade, the prevalence of insect borne diseases due to contaminated food as well as the outbreaks of diseases due to enterotoxin-producing Staphylococcus aureus (ETSA) strains has increased. This study was conducted to determine the prevalence rate, enterotoxigenecity, and antimicrobial resistance of S. aureus isolated from M. domestica collected from the residential areas of nine districts broiler farms in Zabol, Iran. The flies were captured with a sterile nylon net and washed twice with distilled water. The contents were streaked onto selective media and S. aureus was identified using the conventional biochemical tests. Antimicrobial susceptibility testing was performed using CLSI guideline. Staphylococcal enterotoxins (SEs), SEA, SEB, SEC and SED, was detected by the reverse passive latex agglutination (PRLA) method. Coagulase typing was performed with coagulase typing kit. A total of 87 (17%) S. aureus was isolated from 450 samples. The ability to synthesize staphylococcal enterotoxins (SEs) was determined in 62 of 87 (71%) isolates. SE type B was the most common enterotoxin found in the isolated S. aureus (45%), followed by SE type A (26%), SE type C (5%), SE type D (8%), SEA + SEC (7%) and SEA + SEB (7%). Among the antibiotic tested, Penicillin was the most resistant antibiotic tested. Sixty seven percent of isolates belonged to coagulase type III, VI, VII, VIII, IV, and V. Our results suggest that S. aureus, including ETSA, is being carried by house flies such as M. domestica and may contribute to the spread of pathogenic isolates, with an impact on public health.