Sommer Andrew J, Worley Travis K, Sapountzis Panagiotis, Coon Kerri L
Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, USA.
mSystems. 2025 Aug 1:e0021525. doi: 10.1128/msystems.00215-25.
flies are common blood-feeding pests on dairy farms and are suspected carriers of pathogenic bacteria due to their close association with manure and cattle hosts. While prior studies have used amplicon sequencing and culture-dependent methodologies to characterize the composition of the microbiota, little is known about strain-level acquisition of mastitis-causing bacteria from manure by or the functional diversity of -associated taxa. In this study, we address these key knowledge gaps by using whole genome sequencing to provide the first comparative genomic analysis of derived , , and isolates. Our results show that fly and manure isolates collected from the same farm system are phylogenetically interspersed, with subsequent pairwise genome alignments revealing near-identical strains and plasmids shared between the two sources. We further identify a phylogenetic clade of containing known mastitis agents associated with both flies and manure. Functional analysis reveals that this clade is highly enriched in xylose metabolism genes that are rare across other lineages, suggesting potential niche differentiation within the genus. Collectively, our results provide strong evidence for the acquisition of fecal-associated bacteria by adult flies, confirming the link between biting muscid flies and manure habitats. The intermixing of fly and manure isolates in clinically relevant taxonomic groups strongly suggests that flies serve as carriers of opportunistic mastitis-causing or other fecal-borne pathogens and may serve as important vehicles of pathogen dissemination across the dairy farm environment.IMPORTANCEBovine mastitis causes up to $32 billion dollars in losses annually in the global dairy industry. Opportunistic intramammary pathogens can be transmitted through incidental contact with bacteria in environmental reservoirs like manure. However, factors affecting the abundance, persistence, and spread of these bacteria are not well understood. Our research shows that mastitis pathogens are present in the guts of blood-feeding (stable) flies, which develop in cow feces and bite cows. Genomic analysis of isolates from flies, manure, and mastitis cases reveals that strains and antimicrobial resistance genes are shared between these sources. Further analysis of fly gut isolates shows virulence factors and possible niche specialization, identifying fly-associated clades with known mastitis agents from mastitic cows. This strongly suggests that flies play a role in the carriage and circulation of bovine mastitis pathogens from manure in dairy settings.
苍蝇是奶牛场常见的吸血害虫，由于它们与粪便和牛宿主密切相关，被怀疑是病原菌的携带者。虽然先前的研究已经使用扩增子测序和依赖培养的方法来表征微生物群的组成，但对于苍蝇从粪便中获取引起乳腺炎的细菌的菌株水平情况或与之相关的分类群的功能多样性知之甚少。在本研究中，我们通过全基因组测序来填补这些关键的知识空白，首次对从苍蝇、粪便和乳腺炎病例中分离出的菌株进行比较基因组分析。我们的结果表明，从同一农场系统收集的苍蝇和粪便分离株在系统发育上相互穿插，随后的成对基因组比对显示这两种来源之间存在近乎相同的菌株和质粒。我们进一步鉴定出一个包含已知与苍蝇和粪便相关的乳腺炎病原体的葡萄球菌系统发育分支。功能分析表明，该分支在木糖代谢基因方面高度富集，而这些基因在其他葡萄球菌谱系中很少见，这表明该属内可能存在生态位分化。总体而言，我们的结果为成年厩蝇获取与粪便相关的细菌提供了有力证据，证实了吸血蝇类与粪便栖息地之间的联系。在临床相关分类群中苍蝇和粪便分离株的混合强烈表明，苍蝇是机会性乳腺炎病原菌或其他粪源性病原体的携带者，可能是病原体在奶牛场环境中传播的重要媒介。
牛乳腺炎每年给全球乳制品行业造成高达320亿美元的损失。机会性乳房内病原体可通过偶然接触环境储库（如粪便）中的细菌传播。然而，影响这些细菌丰度、持久性和传播的因素尚不清楚。我们的研究表明，乳腺炎病原体存在于吸血厩蝇（厩螫蝇）的肠道中，厩蝇在牛粪中发育并叮咬奶牛。对从苍蝇、粪便和乳腺炎病例中分离出的菌株进行基因组分析表明，这些来源之间共享菌株和抗菌抗性基因。对苍蝇肠道分离株的进一步分析显示出毒力因子和可能的生态位特化，鉴定出与患乳腺炎奶牛中已知乳腺炎病原体相关的苍蝇分支。这有力地表明，厩蝇在奶牛场环境中粪便来源的牛乳腺炎病原体的携带和传播中起作用。
