Evaluation of sporicidal activities of selected environmental surface disinfectants: Carrier tests with the spores of Clostridium difficile and its surrogates

BackgroundThe emergence of Clostridium difficile as a major nosocomial pathogen points to the need for safe, effective, and fast-acting environmental sporicides for infection prevention and control. Available and fast-acting sporicides are generally corrosive and unsafe for both humans and the environment.MethodsWe evaluated chlorine bleach (500 and 5000 ppm) and a gel containing 4.5% of accelerated hydrogen peroxide against the spores of C difficile and its surrogates Bacillus subtilis and Clostridium sporogenes with contact times of 1, 5, and 10 minutes at 20°C ± 2°C using a quantitative carrier test (QCT-2), which is a standard (ASTME2197) of American Society for Testing and Materials International.ResultsThe gel and the higher level of bleach inactivated ≥6-log10 of viable spores of all 3 types in 10 minutes but were unable to do so after 1 and 5 minutes. The lower level of bleach showed virtually no activity even after 10 minutes. The gel could keep the treated surface wet for the entire 10 minutes, whereas the bleach became visibly dry in approximately 4 minutes and needed reapplication.ConclusionThe gel, with no off-gassing and designed especially for use on toilet bowls to allow for the required dwell time on vertical surfaces with one application, is a potential alternative to high levels of bleach.