Differences in milk microbiota between healthy cows and those with recurring Klebsiella mastitis

Abstract Klebsiella spp. infections are an important cause of severe clinical mastitis and recurrent infections, resulting in a poor response to antimicrobial agents and causing substantial economic impacts on the dairy industry. Therefore, investigating underlying causes of Klebsiella spp. infections is essential. Here, we used high-throughput DNA sequencing to characterize the milk microbiota of healthy dairy cows (HDCs) and cows with a history of recurrent Klebsiella mastitis (KLB). Our goal was to identify potential pathogenic genera associated with recurrent Klebsiella infections in cows. Relative abundances of Firmicutes and Faecalibacterium were greater in the KLB group than in the HDC group. In contrast, Proteobacteria and Labrenzia were less abundant than they were in the HDC group. Although species distributions differed between groups, diversity and abundance of communities were comparable. Notably, genera enriched in the KLB group were mostly associated with the intestine, which suggests that cows in the KLB group resided in a contaminated environment or had increased teat-end exposure to fecal bacteria. There were no major differences in microbiota among quarters or between foremilk and milk collected after foremilking. Conversely, the milk of heifers had increased alpha diversity compared to the milk of multiparous cows.