Prevalence of streptomycin and tetracycline resistance and increased transmissible third-generation cephalosporin resistance in Salmonella enterica isolates derived from food handlers in Japan from 2006 to 2021.

This article focuses on the prevalence and antimicrobial resistance (AMR) patterns of Salmonella species isolated from food handlers in Japan between 2006 and 2021. The study found an average Salmonella isolation rate of 0.070%, with shifts in dominant serotypes over time, including Enteritidis, Infantis, Agoueve/Cubana, and Schwarzengrund. Antimicrobial susceptibility testing revealed high resistance rates to streptomycin and tetracycline, and an increasing incidence of cephalosporin resistance mediated by AmpC β-lactamase (AmpC) and extended-spectrum β-lactamase (ESBL) genes such as blaCMY-2 and blaCTX-M-14. Conjugation assays demonstrated that cephalosporin-resistant Salmonella could transfer resistance genes to Escherichia coli via plasmids, notably IncHI1 and IncA/C types, with insertion sequence IS26 implicated in gene mobility. The findings highlight the ongoing risk of transmissible antimicrobial resistance among foodborne pathogens carried by asymptomatic food handlers, underscoring the need for continued surveillance and control measures.