PSVII-9 Microbial characterization of liver abscesses in beef carcasses from the Texas Panhandle using 16S rRNA sequencing.

Abstract Microbiomes refer to the full spectrum of microorganisms within a specific environment and shifts in microbial abundance can influence disease development. Since many bacteria are unculturable in laboratory settings, techniques such as 16S rRNA gene sequencing are essential for profiling microbial communities in complex biological samples. Liver abscesses in cattle, defined by localized bacterial infections in the liver parenchyma, are typically caused by the translocation of gastrointestinal bacteria and can result in reduced animal performance and carcass yield. This study aimed to characterize the microbial communities present in liver abscesses from beef carcasses processed in the Texas Panhandle region using 16S rRNA sequencing. A total of 697 beef carcasses were screened for liver abscesses through random sampling. From these, 15 liver samples (9 abscessed, 6 non-abscessed) were collected and immediately frozen on dry ice. DNA was extracted using the GeneJET Genomic DNA Purification Kit, with quality assessed by agarose gel electrophoresis and quantified using a NanoDrop 2000 Spectrophotometer. The V4 region of the 16S rRNA gene was amplified using primers 515F (5’ GTGYCAGCMGCCGCGGTAA 3’) and 806R (5’ GGACTACNVGGGTWTCTAAT 3’). Library preparation and sequencing were performed using the MR DNA analysis pipeline. Sequences were filtered for quality, dereplicated, denoised, and screened for chimeras. High-confidence sequences were taxonomically classified using BLASTn against a curated NCBI-derived reference database (www.ncbi.nlm.nih.gov). Of the 697 carcasses screened across Texas, New Mexico, Kansas, Colorado, and Oklahoma, 44 tested positive for liver abscesses (6.3%). Positive cases were observed in 32 out of 431 cattle from Texas, 6 of 128 from New Mexico, 2 of 31 from Kansas, and 4 of 94 from Oklahoma. No positive cases were identified from Colorado. Prevalence by sex showed 6 positives among 97 males and 38 among 600 females. Among cattle younger than 30 months, 25 tested positive, while 19 over 30 months were affected. On average, positive liver samples exhibited at least three abscesses. 16S rRNA analysis revealed Fusobacteria and Porphyromonas as the dominant taxa in abscessed liver tissues. Although both healthy and abscessed livers contained microbial populations, these two genera were consistently abundant in abscessed samples. The 6.3% prevalence rate falls within expected global ranges but is lower than initially anticipated. Results suggest that the occurrence of liver abscesses is not significantly influenced by cattle origin, age, or sex. These findings contribute to a broader understanding of microbial dynamics in bovine liver abscesses and support the utility of 16S rRNA sequencing in animal health research.