Stenotrophomonas maltophilia is highly prevalent among houseflies (Musca domestica)

Stenotrophomonas maltophilia is capable of surviving in a wide variety of environments and is considered to be among the antimicrobial-resistant bacteria of greatest public health concern in hospital settings. To clarify the role of houseflies ( Musca domestica ) in disseminating this bacterium, we collected 99 individuals from 15 locations (9 farms and 6 urban areas) in Thailand. S. maltophilia was isolated from 39 % (39/99) of these houseflies, with the isolation rates being similar in farms and urban areas. Multiple-antimicrobial resistance was evident among the S. maltophilia isolates obtained. Of note, the rate of resistance to trimethoprim/sulfamethoxazole (TMP/SMX), the recommended first-line antimicrobial for S. maltophilia infection, was relatively high (30 %). Almost all of the isolates had a different PFGE pattern. These results suggest that houseflies ingest and hos S. maltophilia from several different environmental sources. In conclusion, houseflies may facilitate the spread of antimicrobial-resistant (including TMP/SMX-resistant) S. maltophilia from environmental sources to humans.