Distribution and diversity of Salmonella serovars from beef cattle before, at, and after processing in relation to...

Globally, Salmonella enterica remains a leading cause of foodborne illness, and cattle serve as an important reservoir. Understanding serovar distribution across the beef production continuum and its contribution to human salmonellosis is critical for surveillance and control strategies.

We analyzed Salmonella isolates from cattle (cecal, HACCP, retail meat), and human clinical sources using multivariate approaches, including principal component analysis (PCA), multidimensional scaling (MDS), analysis of similarities (ANOSIM), and permutational analysis of multivariate dispersions (PERMDISP).

Ordination analyses revealed clear ecological structuring of serovars by sampling source. Typhimurium, Newport, and Enteritidis dominated human isolates and exhibited the greatest diversity, consistent with multiple exposure pathways. Retail isolates formed a compact cluster that overlapped with human isolates and were associated with Montevideo and Infantis, suggesting that contaminated retail meat may contribute to human exposure. Cecal and HACCP isolates were the most homogeneous, clustering tightly with serovars such as Cerro, Anatum, Kentucky, Mbandaka, Muenchen, Meleagridis, and Muenster, reflecting stable pre-harvest reservoirs. ANOSIM confirmed significant ecological separation among sources (R = 0.512, p < 0.001), while PERMDISP revealed significantly greater variability among human isolates than among retail, HACCP, and cecal sources.

Salmonella serovar distributions are shaped by sampling sources, with human and retail serovars aligning closely, cecal and HACCP serovars reflecting homogeneous cattle-associated pools, and human cases showing the broadest serovar diversity. These findings highlight retail meat as a critical transmission link, underscore the value and limitations of surveillance, and emphasize the need for integrated monitoring to improve understanding of Salmonella ecology across the One Health interface.