Prevalence of Field-Collected House Flies and Stable Flies With Bacteria Displaying Cefotaxime and Multidrug Resistance

Houseflies (Musca domestica) as vectors of multidrug-resistant, ESBL-producing Escherichia coli in broiler poultry farms of North India: implications for antibiotic resistance transmission

The transmission of antibiotic resistance (AR) from farm animals to healthy human communities, beyond the food chain, is often facilitated by biological vectors, notably houseflies (Musca domestica). This study aimed to evaluate the role of M. domestica collected from commercial broiler chicken farms as a carrier of multidrug-resistant (MDR), extended-spectrum β-lactamase (ESBL)-producing Escherichia coli. E. coli were isolated separately from the housefly's external surface (ES) and internal homogenate (IH) to determine the primary AR transmission route within houseflies. Remarkably, 68.6% houseflies harboured E. coli. Isolated E. coli were evaluated for susceptibility to clinically relevant antibiotics and screened for the presence of 22 plasmid-borne AR genes (ARGs) using PCR. Results revealed significant resistance to key antibiotics, with > 70% of isolates resistant to ampicillin and > 50% resistant to tetracycline and nalidixic acid in both ES- and IH-derived E. coli. Notably, a significant prevalence of resistance was observed to third-generation cephalosporins. Additionally, > 80% of E. coli isolates were MDR. A statistically significant difference (unpaired t-test, p < 0.05) was observed in the presence of ESBL-producing E. coli between the houseflies' ES (28.14%) and IH (38.14%). ARGs such as, ampC, tetA, qnrS, strA, strB, and sul3 were frequently detected in both ES- and IH-derived E. coli isolates. Among the ESBL-producing genes, blaCTX-M was the most abundant. Pearson's correlation analysis predicted the ARGs responsible for phenotypic resistance to specific antibiotics. Farm-derived flies harboured a significantly higher number of MDR E. coli (unpaired t-test, p < 0.05) than the ones isolated from flies housing a distant non-farm environment. Conclusively, this study illustrates the role of houseflies as vectors for AR transmission from AR hotspots to human communities.

Behavioral response of house flies (Diptera: Muscidae) to 3 bittering agents

House flies, Musca domestica L., are pests at livestock facilities. House fly numbers are controlled mainly by manure management and chemical controls, like use of toxic baits. Some toxic baits contain denatonium benzoate as a bittering agent, to avoid poisoning of children. House fly behavioral response to denatonium benzoate was examined, using 2 different diluents, sucrose solution or orange juice. Response of flies to quinine and sucrose octaacetate, 2 other bittering agents, was also examined in sucrose. Sucrose is the sweetener in commercially available toxic house fly baits. The proboscis extension response of both male and female flies was significantly reduced by addition of 1,000 ppm of denatonium benzoate to sucrose. Response in males was also reduced at 100 ppm. Consumption of sucrose by both male and female flies was reduced by addition of 100, 500, and 1,000 ppm of denatonium benzoate, but consumption by males was also reduced at 10 ppm. Addition of sucrose octaacetate had no detectable effect on consumption of sucrose at 100, 500, or 1,000 ppm. In contrast, addition of quinine reduced consumption by both male and female flies in all tested concentrations. In orange juice, 10 ppm of denatonium benzoate is often avoided by children. With orange juice, fly proboscis extension response patterns were the same for both sexes, with a reduction at 1,000 ppm of denatonium benzoate. Orange juice consumption by flies was reduced significantly at 1,000 ppm of denatonium benzoate for females but not at any of the concentrations tested for males.

House Flies Are Underappreciated Yet Important Reservoirs and Vectors of Microbial Threats to Animal and Human Health

House flies are well recognized as filth-associated organisms and public nuisances. House flies create sanitation issues when they bridge the gap between microbe-rich breeding environments and animal/human habitations. Numerous scientific surveys have demonstrated that house flies harbor bacterial pathogens that pose a threat to humans and animals. More extensive and informative surveys incorporating next-generation sequencing technologies have shown that house fly carriage of pathogens and harmful genetic elements, such as antimicrobial resistance genes, is more widespread and dangerous than previously thought. Further, there is a strong body of research confirming that flies not only harbor but also transmit viable, and presumably infectious, bacterial pathogens. Some pathogens replicate and persist in the fly, permitting prolonged shedding and dissemination. Finally, although the drivers still have yet to be firmly determined, the potential range of dissemination of flies and their associated pathogens can be extensive. Despite this evidence, the house flies’ role as reservoirs, disseminators, and true, yet facultative, vectors for pathogens have been greatly underestimated and underappreciated. In this review, we present key studies that bolster the house fly’s role both an important player in microbial ecology and population biology and as transmitters of microbial threats to animal and human health.

Flies as Vectors and Potential Sentinels for Bacterial Pathogens and Antimicrobial Resistance: A Review

The unique biology of flies and their omnipresence in the environment of people and animals makes them ideal candidates to be important vectors of antimicrobial resistance genes. Consequently, there has been increasing research on the bacteria and antimicrobial resistance genes that are carried by flies and their role in the spread of resistance. In this review, we describe the current knowledge on the transmission of bacterial pathogens and antimicrobial resistance genes by flies, and the roles flies might play in the maintenance, transmission, and surveillance of antimicrobial resistance.