NEBULIZATION AND ANTIPSEUDOMONAS AERUGINOSA ACTIVITY OF COLISTIN

Colistin aerosols are frequently administered to patients with cystic fibrosis, However, questions arise concerning the effect of both jet a nd ultrasonic nebulizers on the properties of the drug, The aim of thi s study was to characterize the anti-Pseudomonas aeruginosa (PA) activ ity of colistin after jet (Pari LL(R)) and ultrasonic (DP100(R)) nebul ization. A bench study was performed by capturing the aerosols, determ ining the drug mass, and assessing its anti-PA activity. Because the i nhaled mass of colistin had to be entirely recovered for the bacteriol ogical study, it was assessed by isotopic methods, mixing the drug wit h a Tc-99m-labelled tracer and demonstrating that Tc-99m activity accu rately predicted the mass of colistin. Colistin was extracted from the filters and its antibiotic activity was determined using the method e mployed for the study of the bacteriostatic and bactericidal power of serum on the ATCC 27853 PA strain. The postnebulization minimum inhibi tory concentrations (MIG) were 1.9 mu g.mL(-1) with DP100(R) and 0.5 m u g.mL(-1) with Pari LL(R). These values were less than two dilutions different from the 1 mu g.mL(-1) MIC of non-nebulized colistin, We con clude that neither jet nebulization nor ultrasonic nebulization alter the antibiotic properties of colistin and that both systems can be use d to nebulize colistin.