SPORICIDAL ACTIVITY OF CHLORINE AND PERAC ETIC-ACID ALONE OR ASSOCIATED AGAINST SPORES IN SUSPENSION, FIXED OR IN BIOFILM

In order to assess the sporocidal activity of chlorine and peracetic a cid (PAA), alone and in combination, against a spored biofilm, the bio films of two species (Bacillus subtilis ATCC 6633 and Bacillus megater ium ATCC 8245) were formed on inert support (tygon). A sporulation kin etic of these bacteria in biofilm was established. Sporocidal properti es of chlorine and PAA were compared against free spores, spores fixed by drying and spores in biofilm. The combination of these two product s was also tested. Minimal sporocidal concentrations (MSC) of the two products towards free spores were determined (contact time 5 mn). The efficacy of these MSC were evaluated in terms of contact time on adher ed spores and on spores in biofilm. Chlorine and PAA exhibited an exce llent sporocidal activity. The combination of PAA and chlorine, tested by checkerboard micromethod, was found to be synergistic in case of f ree or adhered spores. The spored biofilm showed a high resistance. Th e combination of these two products revealed then only an additive eff ect.