Serovars and Antimicrobial Resistance of Salmonella in Food Workers and Livestock Products: Insights into Foodborne Transmission Pathways in Eastern Japan

<i>Salmonella</i> is a major cause of infectious enteritis worldwide. In Japan, <i>S</i>. Schwarzengrund, <i>S</i>. Infantis, and <i>S</i>. Thompson are common in broilers and laying hens and are frequently detected in patients with salmonellosis and food workers. Monophasic <i>S</i>. Typhimurium, also found in these populations, often exhibits multidrug resistance. However, multidrug-resistant monophasic <i>S</i>. Typhimurium has not been reported from domestic poultry, suggesting that other livestock products may be potential sources. Therefore, we examined <i>Salmonella</i> prevalence in retail pork, beef, and quail eggs, and characterized isolates from these products and from food workers using serotyping, antimicrobial susceptibility testing, and multilocus sequence typing. <i>Salmonella</i> was highly prevalent in pork liver (43.3%, 13/30) and imported chicken (20.7%, 18/87). Eleven pork liver isolates and two imported chicken isolates (Brazil and Thailand) were multidrug-resistant monophasic <i>S</i>. Typhimurium sequence type (ST) 34. Among 232 isolates from food workers, monophasic <i>S</i>. Typhimurium was the third most frequent serovar, with 63.2% (12/19) being multidrug-resistant ST34. <i>Salmonella</i> was not detected in beef. Hence, food workers may acquire multidrug-resistant monophasic <i>S</i>. Typhimurium ST34 through contaminated pork liver and imported chicken. Thorough cooking of chicken and pork meat, including liver, is essential to reduce the risk of <i>Salmonella</i> transmission.