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

Salmonella is a major cause of infectious enteritis worldwide. In Japan, S. Schwarzengrund, S. Infantis, and S. Thompson are common in broilers and laying hens and are frequently detected in patients with salmonellosis and food workers. Monophasic S. Typhimurium, also found in these populations, often exhibits multidrug resistance. However, multidrug-resistant monophasic S. Typhimurium has not been reported from domestic poultry, suggesting that other livestock products may be potential sources. Therefore, we examined Salmonella 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. Salmonella 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 S. Typhimurium sequence type (ST) 34. Among 232 isolates from food workers, monophasic S. Typhimurium was the third most frequent serovar, with 63.2% (12/19) being multidrug-resistant ST34. Salmonella was not detected in beef. Hence, food workers may acquire multidrug-resistant monophasic S. 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 Salmonella transmission.