Reduced Vancomycin Susceptibility in Clostridioides difficile Is Associated With Specific Ribotypes.

Background: Reduced vancomycin (VAN) susceptibility in clinical Clostridioides difficile isolates is correlated with poor clinical outcomes. However, factors associated with infection with these strains are unknown. The goal of this study was to determine risk factors for reduced VAN susceptibility among clinical isolates of C. difficile.

Methods: This multicenter cohort study included adults with C. difficile infection (CDI) between 2016 and 2021. Clinical C. difficile isolates underwent agar dilution VAN susceptibility testing and ribotyping. Reduced susceptibility was defined as a minimum inhibitory concentration (MIC) > 2 µg/mL. Medical charts were reviewed for host, pathogen, and hospital characteristics and assessed for predictors of reduced VAN susceptibility.

Results: Five hundred and ninety-four hospitalized patients with CDI between 2016 and 2021 (female: 57%, age >65 years: 55%, White/non-Hispanic: 59%, nonsevere CDI episode: 53%) were identified. Of 594 isolates, 173 (29%) had reduced VAN susceptibility (MIC₅₀: 2 µg/mL, MIC₉₀: 4 µg/mL). In multivariable analysis, ribotype (RT) 027 (odds ratio [OR]: 13.4; 95% confidence interval [CI], 7.7-23.4; P < .0001) and RT 255 (OR: 2.9; 95% CI, 1.4-6.1; P = .005) were positively associated with reduced VAN susceptibility whereas RT 014-020 (OR: 0.41; 95% CI, 0.21-0.80; P = .0092) was more likely to be susceptible to VAN. The prevalence of strains with reduced VAN susceptibility increased over time (P = .0163). No patient- or hospitalization-specific variable predicted infection with reduced susceptibility strain.

Conclusions: Certain ribotypes, including RT 027, were the sole independent risk factors for reduced VAN susceptibility. Increased clinical surveillance of these strains, especially RT 027, and their antibiotic susceptibly is warranted to inform prescribing practices.