Prevalence and Characterization of Listeria monocytogenes in Food Court Cold Noodles and Associated Contact Surfaces in Korea.

Listeria monocytogenes is a foodborne pathogen that can survive at refrigerated temperatures. However, data on L. monocytogenes contamination in food court settings are lacking. We investigated the prevalence and characteristics of L. monocytogenes in cold food court noodles and their manufacturing environments in South Korea. One hundred eighty-two samples, including 168 ready-to-eat (RTE) cold noodle products, 1 noodle, 1 cold noodle broth, 4 garnishes, and 8 environmental swab samples, were collected from 44 large supermarket food courts and analyzed to isolate L. monocytogenes. Isolation was performed through selective enrichment followed by plating on PALCAM and ALOA agar, and identification was confirmed by PCR. Serotyping was performed using conventional antisera agglutination and PCR-based serogrouping, and molecular characterization was conducted through multilocus sequence typing (MLST) using seven housekeeping genes, detection of ten virulence genes by PCR, and antibiotic susceptibility testing using the E-test method. Listeria monocytogenes was exclusively isolated from the cold noodle broth of six samples. Serotyping identified three serotypes (1/2a, 1/2b, and 1/2c), predominantly belonging to Lineage II, and MLST classified the isolates into ST9 and ST87, which are associated with food processing environments and linked to human infections, respectively. All isolates carried multiple virulence genes and exhibited resistance to ciprofloxacin, clindamycin, oxacillin, and tetracycline while remaining susceptible to β-lactam antibiotics and vancomycin. These findings underscore the critical need for rigorous hygiene management in the production and distribution of cold noodles, particularly in the handling of cold noodle broth. Given the persistence of L. monocytogenes in food-processing environments, continuous monitoring and enhanced sanitation protocols are essential to mitigate contamination risks in RTE food products.