[Bactericidal efficacy of a disinfectant by AFNOR standards NF T 72-150 and NF T 72-151. A collaborative study]

In this collaborative study, 23 French laboratories measured the bactericidal activity of the same disinfectant, a phenolic compound, on 3 bacterial strains (P. aeruginosa, S. aureus, and M. smegmatis), by AFNOR standards NF T 72-150 (dilution-neutralization method) and NF T 72-151 (membrane filtration method). Minimal bactericidal concentrations determined by both methods were identical or very similar (deviation by one dilution only). Thus, both standard methods produce the same results. Only three laboratories gave erroneous results. The twenty others found bactericidal concentrations which can be considered as correct (between half and double of calculated mean) in 80 to 95% of cases, depending on methods and strains. It may be estimated that 8 laboratories out of 10 master AFNOR techniques for evaluation of antiseptics and disinfectants.