Bacterial communities and prevalence of antibiotic resistance genes carried within house flies (Diptera: Muscidae) associated with beef and dairy cattle farms

Authors: NEUPANE, SARASWOTI - Kansas State University; TALLEY, JUSTIN - Oklahoma State University; Taylor, David; Nayduch, Dana

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2023
Publication Date: 8/23/2023
Citation: Neupane, S., Talley, J., Taylor, D.B., Nayduch, D. 2023. Bacterial communities and prevalence of antibiotic resistance genes carried within house flies (Diptera: Muscidae) associated with beef and dairy cattle farms. Journal of Medical Entomology. Article tjad112. https://doi.org/10.1093/jme/tjad112.
DOI: https://doi.org/10.1093/jme/tjad112

Interpretive Summary: House flies carry harmful bacteria at livestock operations which are acquired from sources in their environment such as animals and their waste. The types and abundances of different bacteria carried within flies tightly correlates with the time and location where they are collected, and varies across geographic areas. This study determined the differences in the types (species) of bacteria carried in house flies collected from beef feedlots and dairy farms in Oklahoma, Kansas and Nebraska. "Snapshots" of their bacterial communities, including the number and types of species present in flies, was affected by farm type and state. Less than half of the bacteria species found in individual flies were the same in flies from any location. However, these species comprised over 90% of the total bacteria carried within the flies which means that the most highly abundant species were shared among flies but that >50% of the other bacterial species flies carry, while low abundance, are correlated with their particular habitat (farm type or state). Furthermore, flies carried many types of bacteria that can cause diseases such as food-borne illnesses in humans and pink eye or bovine respiratory disease in cattle. The prevalence of the pink eye pathogens was greater in flies from beef feedlot operations than those from dairy farms. Finally, flies also carried antibiotic resistance genes, including multiple variations of tetracycline resistance genes and one type of florfenicol resistance gene, indicating that some of the bacteria they carry are resistant to drugs commonly used in animal production. This study provides strong evidence supporting the role of house flies as sources and transmitters of bacterial threats to human and animal health in cattle operations.

Technical Abstract: House flies (Musca domestica Linnaeus) are vectors of human and animal pathogens at livestock operations. Microbial communities in flies are acquired from, and correlate with, their local environment. However, variation among microbial communities carried by flies from farms in different geographical areas is not well understood. We characterized bacterial communities of female house flies collected from beef and dairy farms in Oklahoma, Kansas, and Nebraska using 16S rDNA amplicon sequencing and PCR. Bacterial community composition in house flies was affected by farm type and location. While the shared number of taxa between flies from beef or dairy farms was low, those taxa accounted >97% of the total bacterial community abundance. Bacterial species richness was 4% greater in flies collected from beef than in those collected from dairy farms and varied by farm type within states. Several potential pathogenic taxa were highly prevalent, comprising a core bacterial community in house flies from cattle farms. Prevalence of the pathogens Moraxella bovis and Moraxella bovoculi was greater in flies from beef farms relative to those collected on dairy cattle farms. House flies also carried bacteria with multiple tetracycline and florfenicol resistance genes. This study suggests that the house flies are significant reservoirs and disseminators of microbial threats to human and cattle health.