101 Fusobacteria,Bacteroidetes, and more! Linking the Microbial Communities in Bovine Liver Abscesses to the Gut

Abstract

Abstract Liver abscesses (LAs) are a common and important problem in cattle because of their association with decreased growth and production, low carcass quality, and the significant economic losses associated with liver condemnation. Fusobacterium necrophorum has traditionally been considered the primary etiologic agent of LA formation in cattle, but recent evidence has demonstrated that LA microbial communities are far more polymicrobial than previously believed. Here, we characterize microbial communities within multiple LAs from the same animal, provide evidence that some LAs may be seeded from the hindgut, identify biomarkers throughout the gut-liver axis that predict the presence of LAs, and demonstrate the impact of tylosin on microbial communities in the rumen, ileum, and colon. 16S rRNA gene sequencing was used to characterize communities from LA purulent material, as well as from the luminal and epithelia, communities in three gut locations (rumen, ileum, colon) within the same animals. A combination of QIIME2 and phyloseq were used to analyze sequence data, and microbial community composition was compared based on generalized UniFrac distances. Taxa discriminant of LA occurrence were identified using linear discriminant analysis effect size (LEfSe). Despite being the most abundant genus when averaged across all LA communities, Fusobacterium spp. was not the predominant taxa in the majority of LAs. In fact, members of Bacteriodetes (largely Bacteroides, Porphyromonas) were the predominant taxa in more than one-half of all LA communities. Importantly, multiple LAs from the same animal had remarkably similar community structure, and multiple taxa including Bifidobacterium spp., widely considered beneficial to gut barrier function in humans, were differentially abundant in both the foregut and hindgut between cattle that did and did not have LAs. Further, tylosin had little impact on the diversity and composition of microbial communities within LAs but did alter communities in the rumen and small intestine. In particular, members of the family Lachnospiraceae were more abundant in the rumen and hindgut of animals given tylosin. Together, these results provide additional evidence challenging the traditional theory of LA etiology (that bacterial translocation occurs exclusively from the rumen) and provides evidence that barrier dysfunction in the gut may be the underlying cause of LA formation.