Differences in Salmonella Serotypes in Broiler Chickens Within and Between Slaughter Establishments in the United States

There are more than 2500 serotypes of Salmonella enterica. One interesting feature of this bacterium is that regardless of whether samples are collected from food commodities, a single animal species, humans, or a specific environmental setting, only about 5 serotypes constitute 50% or more of all positive samples. Another interesting feature of Salmonella is that the most common serotypes are not consistent across time or broad geographic region. Examples of this phenomenon are that Salmonella Heidelberg was the third most common serotype found in United States human illness cases in 1996, but the 53rd most common serotype in 2022. An example of serotype-specific spatial clustering is the occurrence of Salmonella Weltevreden predominantly in continental Southeast Asia. Clustering in space and time presents opportunities to control more pathogenic serotypes. In this study, data from a seven-month survey of broiler chicken carcass production in the United States are used to assess how the occurrence of the dominant serotypes changes as carcasses move through the production process. Samples were collected at rehang and postchill, with the number of positive samples at each location being 2909 and 233, respectively. Different intervention strategies may impact specific serotypes differently. Additional analyses demonstrate how serotypes are clustered (or not) as a function of production volume and corporate ownership. Understanding how the occurrence of serotypes varies across the industry can provide insights into factors that lead to the clustering of specific serotypes and has the potential to help identify intervention strategies that effectively reduce the risk of human salmonellosis.