[Kinetics of bactericidal and sporicidal effects of a disinfectant against bacteria isolated from hospital units].

The bactericidal and sporicidal activities of a peracetic acid disinfectant commonly used in hospitals (Acetoper 200) was studied using three bacterial species recovered in water from hemodialysis machines and humidifiers, i.e., Pseudomonas aeruginosa, Serratia liquefaciens, and Bacillus subtilis (spores). The method used was derived from AFNOR norms NF T 72-151 and NF T 72-231. For each strain, three concentrations of disinfectant were tested. Counts were performed every five minutes for one hour to evaluate killing kinetics. For both Gram-negative organisms, survival curves were biphasic, whereas B. subtilis counts decreased logarithmically. Both concentration and time influenced the 5 log10 decrease in counts. With S. liquefaciens and B. subtilis (spores), the 5 log10 decrease was not reached with low levels of disinfectant. In every case, the D value decreased substantially with increasing levels of disinfectant.