The effectiveness of sodium dichloroisocyanurate treatments against Clostridium difficile spores contaminating stainless steel

Background: Clostridium difficile is a major cause of hospital-associated infective diarrhea, and its spore form can persist for months in the hospital environment. Chlorine-based cleaning agents are recommended for eliminating this reservoir of potential infection. Objectives: To investigate the individual contributions of active chlorine, detergent and mechanical action on decontamination of a C difficile contaminated surface. Methods: C difficile spores in test soil were dried onto stainless steel strips and exposed to sodium dichloroisocyanurate (NaDCC) or NaDCC combined with detergent (NaDCC+) or exposed to these cleaning formulations combined with wiping and/or detergent precleaning. After set contact times, remaining viable spores from the strips were recovered and enumerated by vortexing with glass beads, followed by membrane filtration. Results: Compared with NaDCC, the inclusion of detergent in the NaDCC+ formulation did not improve the effectiveness of decontamination in any exposure-only treatment at concentrations tested (P > .05). Combining wiping with exposure to the cleaning formulations improved decontamination effectiveness with further reductions in spore counts of 1.66- and 2.19-log ₁₀ colony-forming units at 2 and 20 minutes, respectively, using NaDCC, and of 2.46 and 2.56 log₁₀ colony-forming units at 2 and 20 minutes, respectively, using NaDCC+. Precleaning the strips by wiping with detergent before exposure to NaDCC was more effective than wiping with NaDCC or NaDCC+ at 10 and 20 minutes contact times. Wiping with NaDCC+ was more effective than NaDCC only at a 2-minute contact time. Wiping with detergent followed by subsequent wiping with NaDCC (1,000 ppm) was the most effective treatment tested with a 4.00-log₁₀ reduction observed. Conclusion: Rigorous precleaning with detergent and the associated physical removal of spores through the mechanical action associated with wiping are important factors in achieving effective decontamination of surfaces when using chlorine-based agents.