Prevalence, genetic diversity, and drug-resistance of Listeria monocytogenes ST8 in enoki mushrooms: Comparative genomic and phenotypic analysis with meat and clinical ST8 isolates.

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Citation abstract

Listeria monocytogenes is a significant foodborne pathogen. Enoki mushrooms, as an important pollution source, has attracted people's attention in recent years. This study investigated the contamination of L. monocytogenes in enoki mushroom samples, multilocus sequence typing (ST), and drug resistance. Furthermore, the dominant ST8 strain from the enoki mushroom source was selected as the object to analyze its OD 590 values and in vitro virulence level. Results showed that L. monocytogenes contamination rate in enoki mushroom samples collected from Shanghai was 46%, with 53 of 65 isolates belonging to ST8. The SNP differences of the ST8 strain range from 0 to 97. Antibiotic susceptibility testing of the 65 strains from enoki mushroom revealed that all isolates were resistant to Oxacillin but not resistant to Clindamycin, Chloramphenicol, and Ciprofloxacin. The crystal violet staining results showed that the ST8 strains had higher OD 590 under nutrient-rich conditions compared to nutrient-restricted conditions. In vitro cellular model experiments revealed that ST8 strains exhibited higher adhesion and invasion rates in JEG-3 cells, while their adhesion and invasion capabilities in HepG-2 cells were relatively lower. The strains from the enoki mushroom source did not show significant differences in OD 590 values compared with clinical and ready-to-eat (RTE) meat strains in TSB-YE and 10% TSB-YE. Strains derived from enoki mushrooms and RTE meats exhibited significantly higher invasion to JEG-3 cells compared with clinical strains. These findings indicate that enoki mushrooms are susceptible to contamination by L. monocytogenes, and the ST8 strain isolated from this sources exhibited multidrug resistance and possesses pathogenic potential.