Evaluating the Aquatic Environment as a Reservoir for Salmonella: A Comparative Analysis with Clinical Strains

Aquatic environments are potential reservoirs for the persistence and spread of pathogenic bacteria. This study investigated the prevalence of Salmonella spp. in stream environments and their relationship with clinical isolates in Republic of Korea. A total of 4582 water samples were collected from 94 streams. We identified these isolates using MALDI–TOF MS and the Kauffmann–White scheme. Polymerase chain reaction and sequencing were performed to identify the resistance genes. Whole genome sequencing analysis and pulsed-field gel electrophoresis (PFGE) were performed to investigate genetic relatedness. In total, 110 Salmonella isolates showing 23 serotypes were isolated from the streams. S. Typhimurium (20.9%) was the most common, followed by S. Livingstone (17.3%), S. Infantis (10.9%), S. Othmarschen (6.4%), S. I. 4,[5],12:i:- (5.5%), and S. Thompson (5.5%). PFGE patterns of eight serotypes were identical or closely related to the stream and clinical strains. The sequence types of S. Mbandaka and S. Livingstone isolates from streams were identical to those of the clinical specimens as ST413 and ST543, respectively. Salmonella strains are highly prevalent in streams and are closely related to the isolates obtained from patients. Therefore, the continuous monitoring of stream environments is required to control the spread of Salmonella.