Efficacy of UV-C 254 nm Light and a Sporicidal Surface Disinfectant in Inactivating Spores from Clostridioides difficile Ribotypes In Vitro

Abstract

Clostridioides difficile is widely recognised as one of the most common causes of healthcare-associated C. difficile infections due to the ability of spores to survive for prolonged periods in the hospital environment. This study aimed to evaluate the efficacy of UV-C 254 nm light in the inactivation of the spores of different C. difficile ribotypes on brain heart infusion (BHI) agar plates or in phosphate-buffered saline (PBS) with varying spore densities. Furthermore, the effectiveness of a sporicidal surface disinfectant against C. difficile spores was determined on different surfaces. Spore suspensions of different C. difficile strains in the range of 10⁵-10⁷ colony-forming units (CFUs) mL^-1 were inoculated on BHI agar plates or in PBS and exposed to UV-C light for up to 30 min. Additionally, a spore suspension of 10³-10⁵ CFUs was spread over a 1 cm² test area on different surfaces, and sporicidal surface wipes were used according to the manufacturer's instructions. The findings demonstrated that spores of C. difficile ribotypes exhibited a complete reduction in log₁₀ CFU on BHI agar plates and PBS following 20 min of exposure to a UV-C dose of 2208 mJ cm^-2. The surface wipes with sporicidal properties demonstrated efficacy in reducing the number of C. difficile spores on the Formica, stainless steel, and plastic surfaces by 2.03-3.53 log₁₀. The present study demonstrates that moist surfaces or liquids can enhance the efficacy of UV-C treatment in reducing C. difficile spores. This approach may be applicable to the surfaces of healthcare facilities and to water disinfection systems.

Keywords: Clostridioides difficile; UV-C light; disinfectant; ribotypes; spores; sporicidal; sporicidal surface wipes.

Figure 1

Intensities of UV-C 254 nm mercury lamps used in this study during the first 90 min exposure. Error bars represent the standard errors of the mean from three independent measurements.

Figure 2

Schematic diagram of the experimental setup used to determine the efficacy of UVC 254 nm light on the spore germination ability of different C. difficile RT strains inoculated on the surface of BHI agar plates (A) and in PBS solution (B).

Figure 3

Schematic diagram of the experimental setup used to determine the efficacy of sporicidal surface wipes on the survival and germination ability of spores of different C. difficile RT strains.

Figure 4

Recovery and germination ability of spores from five different C. difficile PCR ribotypes when exposed to UV-C 254 nm light on the surface of BHI agar plates after various exposure times. Each bar represents the mean of three replicates ± standard deviation. p < 0.0001 (****), p < 0.001 (***), p < 0.01 (**).

Figure 5

Recovery and germination ability of spores from five different C. difficile RT strains when exposed to UV-C 254 nm light in PBS solution for varying exposure times. Each bar represents the mean of three replicates ± standard deviation. p < 0.0001 (****), p < 0.01 (**).

Figure 6

Log₁₀ CFU reduction of spores from five different C. difficile ribotypes on the surface of BHI agar plates (A) and in PBS solution (B). Respective spores were exposed to UV-C light at various doses (1104 to 3312 mJ cm⁻²). The error bars represent the standard errors of the mean from independent experiments (n = 3).

Figure 7

Inactivation of spores derived from different C. difficile ribotypes on different surfaces treated with sporicidal surface wipes. The mean of three replicates ± standard deviation is shown for each error bar. Significant differences (p < 0.05) between strains are indicated by different letters.