Getting real with disinfectant concentration and contact time


The processes in place for establishing whether a hospital disinfectant is suitable for use in a clinical setting have been around for a long time - but do they remain fit for purpose? A recent study shows that disinfectant concentration and contact time can be reduced without negatively affecting efficacy - but not too much!

Tests with unrealistically long contact times, high concentrations of disinfectant, and performed in suspension rather than on a hard substrate are not helpful in establishing whether a disinfectant is suitable for use in the clinical setting. Equally, laboratory disinfectant testing needs to be performed with a worst-case scenario in mind. A recent study 'stress tested' the parameters for the laboratory testing of a selection of hospital disinfectants, reducing the disinfectant concentration and contact time. The disinfectants tested were accelerated hydrogen peroxide, quaternary ammonium compounds (QACs), and sodium hypochlorite. There was a degree of tolerance to reducing contact time and disinfectant concentration. The study found that bactericidal efficacy was not reduced when contact times or concentrations were reduced to just below label use values. However, all of the disinfectants were significantly less bactericidal when contact times and concentrations were reduced substantially. The sodium hypochlorite was most tolerant to changes in contact time and concentration.

This study is useful and suggests that contact times and disinfectant concentrations could be reduced in some settings. However, there are many drivers of the efficacy of a disinfectant, including soiling, the presence of biofilms, and stability of the disinfectant. Therefore, laboratory studies need to be complemented by real-world studies in the clinical setting to establish the suitability of disinfectants for surface disinfection in hospitals.