A molecular study of the Salmonella enterica serovars Abortusovis, Typhimurium, and Enteritidis

Abstract

This study presents a molecular analysis of 3 important human and animal serovars of Salmonella: Typhimurium, Enteritidis, and Abortusovis. We also provide information that can be applied in the surveillance of salmonellosis. Over the course of 3 decades, 90 isolates were collected, with 30 isolates representing each type of serovar. In addition to conventional serotyping, serovars were confirmed by polymerase chain reaction (multiplex PCR and IS200 PCR). Pulsed-field gel electrophoresis (PFGE) of the serovars confirmed 12, 15, and 20 patterns, respectively. In an analysis of the results, 5 pulsotypes (80% of isolates) of Salmonella Typhimurium and 4 pulsotypes (64% of isolates) of Salmonella Enteritidis were confirmed to be prevalent, and Salmonella Abortusovis showed unexpectedly high diversity, with just 2 prevalent pulsotypes (40% of isolates). S. Enteritidis and S. Abortusovis were identified as polyphyletic (possibly the first report), while S. Typhimurium was identified as monophyletic. The combination of PFGE, random amplified polymorphic DNA-PCR (RAPD-PCR) with 2 primers, and antibiotic susceptibility tests showed 29, 23, and 21 distinct patterns in the serovars, respectively; for this combination of methods, the value of the discrimination index was established at more than 0/95 in each serovar. The results of this study indicate that this combination of methods can increase the discrimination index. It is therefore suitable and applicable for use in a Salmonella surveillance system, especially in endemic regions in which there is no active surveillance system or information.