Risk of Antimicrobial Resistant Non-Typhoidal Salmonella during Asymptomatic Infection Passage between Pet Dogs and Their Human Caregivers in Khon Kaen, Thailand

To explore the risk of antimicrobial resistant (AMR) non-typhoidal Salmonella during asymptomatic infection passage between pet dogs and human caregivers in Khon Kaen, Thailand, one hundred forty paired fecal samples (n = 280) were obtained from companion dogs and their human caregivers, interviewed from 140 households during 2019–2020. The purified Salmonella isolates were serotype-identified and tested for antimicrobial resistance against ampicillin, ciprofloxacin, chloramphenicol, nalidixic acid, streptomycin, sulfamethoxazole–trimethoprim, and tetracycline. The homologous Salmonella isolate pairs (suggesting Salmonella infections may have been due to passage between each one of the pair, or derived from the same source) were subsequently characterized by serotype screening, pulsed field gel electrophoresis (PFGE), and Synchrotron Fourier transform infrared spectroscopy (SR-FTIR). The Salmonella prevalence observed in dogs, 12.86% (18/140), was not significantly different from that observed in humans, 17.86% (25/140) using McNemar’s test. The AMR patterns (the patterns among the isolates of pet dogs and caregivers) and the serotypes (thirteen serotypes with 18 isolates from pet dogs plus thirteen serotypes with 25 isolates from humans) between pet dogs and humans were not significantly different using Pearson’s chi-squared test. The homologous Salmonella isolates from the Salmonella-present households was 5.13% (2/39). This study demonstrated that the hypothesis that there is a high risk of Salmonella infection passage between dogs and humans with close contact in Khon Kaen is doubtful. Only 5.13% of homologous Salmonella isolates from Salmonella-present households were found in Khon Kaen, Thailand, although the prevalence of Salmonella-positive samples, serotypes, and antimicrobial resistance patterns were quite similar among the two populations.