Polymerase chain reaction for the in vitro detection of the pESI plasmid associated with the globally circulating Salmonella Infantis outbreak strain

Abstract

A globally circulating strain of Salmonella enterica serotype Infantis containing the pESI plasmid has increased in prevalence in poultry meat samples and cases of human infections. In this study, a polymerase chain reaction (PCR) protocol was designed to detect the pESI plasmid and confirm the Infantis serotype of Salmonella isolates. Primers were tested bioinformatically to predict specificity, sensitivity, and precision. A total of 54 isolates of Salmonella serotypes Infantis, Senftenberg, and Alachua were tested, with and without the pESI plasmid carriage. Isolates of 31 additional serotypes were also screened to confirm specificity to Infantis. Specificity, sensitivity, and precision of each primer were >0.95. All isolates tested produced the expected band sizes. This PCR protocol provides a rapid and clear result for the detection of the pESI plasmid and serotype Infantis and will allow for the in vitro detection for epidemiological studies where whole-genome sequencing is not available. Significance and impact of the study Salmonella enterica serotype Infantis containing the pESI plasmid is one of the most common strains of Salmonella isolated from chicken meat products around the world and causes numerous human infections. This plasmid contains genes that could provide carriers an advantage in a poultry or human host. Detecting this plasmid is of utmost importance for epidemiological investigations. The presented assay uses fewer targets than previously published detection schemes and provides an alternative detection method to whole-genome sequencing.