Colonization, Molecular Epidemiological Characteristics, Antimicrobial Resistance, and Related Risk Factors of Clostridioides difficile in Elderly Hospitalized Patients

Abstract Objective: To investigate the colonization status, molecular epidemiological characteristics, antimicrobial resistance profiles, and risk factors for Clostridioides difficile ( C. difficile ) colonization in elderly hospitalized patients, and to provide evidence for clinical prevention and control. Methods: A total of 300 elderly inpatients admitted to geriatric wards between January 2022 and December 2024 were enrolled. Inclusion criteria were age ≥65 years, hospital stay ≥72 h, complete clinical data, and absence of diarrhea with normal stool appearance upon admission. Patients without stool specimens or who refused specimen collection were excluded. Stool specimens were collected for C. difficile isolation and identification. The toxin genes tcdA and tcdB were detected by PCR. Multilocus sequence typing (MLST) was performed for molecular epidemiological analysis. The agar dilution method was used to determine minimum inhibitory concentrations (MICs) for nine antimicrobial agents. Clinical data were collected; univariate and multivariate logistic regression analyses were applied to identify risk factors for C. difficile colonization. Results: Among the 300 elderly inpatients, 95 (31.67%) were colonized with C. difficile . Of the 95 isolates, 41 (43.16%) were non-toxigenic (tcdA-/tcdB-), and 54 (56.84%) were toxigenic. All toxigenic strains were tcdA+/tcdB+, and no tcdA-/tcdB+ strains were detected. The 95 isolates were assigned to 15 sequence types (STs). ST81 was predominant (28 isolates, 29.47%), followed by ST39 (18 isolates, 18.95%). All isolates were susceptible to vancomycin and metronidazole. Univariate analysis showed that older age, immunocompromised status, longer hospital stay, and antibiotic exposure were significantly associated with C. difficile colonization (P < 0.05). Multivariate logistic regression confirmed older age, immunocompromised status, prolonged hospital stay, and antibiotic exposure as independent risk factors for C. difficile colonization (P < 0.05). Conclusion: The C. difficile colonization rate among elderly hospitalized patients is relatively high; ST81 and ST39 as major genotypes, with toxigenic strains accounting for 56.84% of isolates. Older age, immunocompromised status, longer hospital stay, and antibiotic exposure are independent risk factors for C. difficile colonization. Vancomycin and metronidazole remain preferred agents for empirical CDI therapy. High resistance rates were observed for cephalosporins, clindamycin, and ciprofloxacin; these agents are not recommended for CDI treatment. Caution should be exercised when extrapolating susceptibility results from asymptomatic colonizing isolates to clinical CDI infections.