Genomic insights into Listeria monocytogenes in Chengdu catering facilities: disinfectant tolerance and stress adaptation mechanisms.

Listeria monocytogenes poses a significant threat in food service environments due to its environmental robustness and pathogenicity. In this study, L. monocytogenes contamination across 24 catering facilities in Chengdu highlighted potential public health concerns, with a 6.43% (40/622) prevalence rate and meat processing areas as primary hotspots (13.48%, 19/141; cleaned meat: 25.0%, 6/24; cleaning pools: 20.83%, 5/24). Cross-contamination pathways from raw to cooking area were identified in 25% of facilities. Genomic characterization showed serotype 1/2a dominance (65.0%, 26/40), with 82.5% (33/40) of isolates belonging to serogroups frequently associated with human invasive listeriosis (1/2a, 1/2b), while ST101 (20.0%, 8/40) and ST121 (17.5%, 7/40) exhibited broad spatial dissemination. All isolates harbored disinfectant tolerance genes (Ide/mdrL: 100%) and stress adaptation markers (fosX: 100%; cspB/D/dnaK: 100%). Phenotypic antibiotic resistance was low (meropenem: 12.5%, 5/40; tetracycline: 2.5%, 1/40). Disinfectant efficacy testing exposed critical gaps: NaClO MICs (750-3,000 μg/mL) exceeded recommended food contact surface concentrations (240 μg/mL) by 3-12.5-fold, whereas QACs (MIC: 3.91-7.81 μg/mL) and H2O2 (MIC: 187.5-375 μg/mL) demonstrated high efficacy, with applied concentrations exceeding MICs by 64-128-fold and approximately 53-128-fold, respectively. These findings reveal a disconnect between the reduced in vitro susceptibility of prevalent strains to commonly used chlorine-based disinfectants and the high efficacy observed for QACs and H2O2. This integrated genomic-phenotypic approach identifies high-risk contamination nodes, highlighting its potential to inform the development of targeted control strategies for food service operations.