Clinical and molecular epidemiology of Clostridioides difficile infection in a county-level hospital in Zhejiang Province, China.

BACKGROUND: Clostridioides difficile infection (CDI) remains an important healthcare-associated infection worldwide. However, the molecular epidemiology of CDI in county-level hospitals across China remains poorly understood. Therefore, this study aimed to investigate the clinical and molecular epidemiology of CDI in a county-level hospital in Zhejiang Province, China. METHODS: Between January and December 2025, we conducted a genomic epidemiology study of C. difficile isolates recovered from patients with clinically suspected CDI at a county-level hospital in Zhejiang Province, China. C. difficile strains were isolated and identified, typed by multi-locus sequence typing (MLST), and phylogenetic analysis, core-genome single-nucleotide polymorphism (cgSNP) analysis, and antimicrobial resistance (AMR) genes identification were extracted from whole genome sequencing. Antimicrobial susceptibility testing was performed using the agar dilution method according to CLSI guidelines. Statistical analysis was performed using R/Python. RESULTS: In total, 50 (3.8%) toxigenic C. difficile isolates were identified from a total 1,315 stool samples. Among them, 40 (80.0%) exhibited the tcdA+/tcdB+/CDT- profile, 8 (16.0%) exhibited the tcdA-/tcdB+/CDT- profile, and 2 (4.0%) exhibited the tcdA+/tcdB+/CDT+ profile. And 16 (32.0%) strains were isolated from the Digestive department, followed by 8 (16.0%) strains from the Rehabilitation department. The most sequence type of the toxigenic C. difficile was ST2 (14.0%) and ST3 (14.0%), followed by ST81 (12.0%), ST35 (10.0%) and ST129 (8.0%). cgSNP-based minimum spanning tree analysis provided genomic evidence compatible with potential nosocomial transmission, including ST3, ST35, ST81, and ST129, with closely related isolates identified both within and between departments. Furthermore, all toxigenic isolates were successfully analyzed for antimicrobial susceptibility phenotype and remained susceptible to vancomycin, metronidazole, tigecycline, daptomycin, and fidaxomicin. High resistance rates were observed for clindamycin and erythromycin, while moderate resistance to tetracycline and moxifloxacin was also detected. Resistance phenotypes generally correlated with the presence of corresponding resistance determinants, including ermB, tetM, and the gyrA (Thr82Ile) mutation. CONCLUSIONS: This study provides insight into the molecular epidemiology and antimicrobial resistance characteristics of toxigenic C. difficile in a county-level hospital in China. Our findings show potential healthcare-associated transmission of several predominant lineages and highlight the importance of continuous genomic surveillance and strengthened infection prevention and control strategies to limit the dissemination of epidemic and multidrug-resistant C. difficile strains in healthcare settings.