Efficacy of copper-impregnated antimicrobial surfaces against Clostridioides difficile spores

Clostridioides difficile (C. difficile) is one of the most common causes of healthcare-associated infections (HAIs). Elimination of C. difficile spores is difficult as they are resistant to common hospital-grade disinfectants. Copper-impregnated surfaces provide continuous reduction of multiple pathogens, potentially lowering the risk of infections. This manuscript aims to evaluate the efficacy of copper-impregnated surfaces on C. difficile spores.

Control (no copper) coupons and copper coupons containing 20% copper-oxide were inoculated with C. difficile spore loads ranging from 10⁵ to 10⁷ spores, with or without 5% fetal bovine serum soil load. After 4 hours of contact time, the C. difficile spores were recovered, plated on C. difficile growth media, and colony forming units were counted. The efficacy of copper (log₁₀ kill) was estimated using a Bayesian latent variables model.

After 4 hours, unsoiled copper bedrail and copper table coupons at mean spore inoculation resulted in a 97.3% and 96.8% reduction in spore count (1.57 and 1.50 log₁₀ kill, respectively). That of soiled bedrail and table coupons showed a 91.8% and 91.7% reduction (1.10 and 1.10 log₁₀ kill, respectively).

Copper coupons can substantially reduce C. difficile spores after 4 hours, but results vary depending on the initial spore concentration and presence or absence of organic material. Higher initial spore loads or excess organic material may prevent spores from contact with copper surfaces, thus decreasing kill efficacy. Continuous sporicidal effect of copper-impregnated surfaces may decrease spore burden and help prevent transmission of spores.