Clinical Characteristics, Antimicrobial Resistance, Virulence Genes and Multi-Locus Sequence Typing of Non-Typhoidal Salmonella Serovar Typhimurium and Enteritidis Strains Isolated from Patients in Chiang Mai, Thailand

Abstract

Non-typhoidal <i>salmonellosis</i> (NTS) caused by ingesting <i>Salmonella enterica</i> contaminated food or drink remains a major bacterial foodborne disease. Clinical outcomes of NTS range from self-limited gastroenteritis to life-threatening invasive NTS (iNTS). In this study, we isolated <i>Salmonella</i> spp. from the stool and blood of patients hospitalized at Maharaj Nakorn Chiang Mai Hospital, Chiang Mai, Thailand, between 2016-2021 (a total of 395 cases). Then, serovar Typhimurium and Enteritidis were identified and further characterized by multiplex PCR, and multi-locus sequence typing. Our data show that multidrug resistance (MDR) sequence type 34 (ST34) and ST11 are the predominant sequence types for serovars Typhimurium and Enteritidis, respectively. Most <i>S. Typhimurium</i> ST34 lacks <i>spvB</i>, and most <i>S. Enteritidis</i> ST11 harbor <i>sseI</i>, <i>sodCI</i>, <i>rpoS</i> and <i>spvB</i> genes. NTS can be found in a wide range of ages, and anemia could be a significant factor for <i>S. Typhimurium</i> infection (86.3%). Both <i>S. Typhimurium</i> (6.7%) and <i>S. Enteritidis</i> (25.0%) can cause iNTS in immunocompromised patients. <i>S. Typhimurium</i> conferred MDR phenotype higher than <i>S. Enteritidis</i> with multiple antibiotic resistance indexes of 0.22 and 0.04, respectively. Here, we characterized the important <i>S. Typhimurium</i>, <i>S. Enteritidis</i>, and human clinical factors of NTS within the region.