Microbial contamination of nebulization solution and its measures

We evaluated the microbial contamination of nebulization solutions in medication cups from a total of 76 ultrasonic nebulizers in use in 10 hospitals. In addition, an interview survey was given to nurses to evaluate the disinfection methods of these ultrasonic nebulizers. Of a total of 76 nebulization solution samples, 11 (14.5%) were contaminated with 10-10(2) colony-forming units (CFU)/ml and 9 (11.8%) with 10(3)-10(5) CFU/ml. The major contaminants were glucose non-fermentative bacilli such as Burkholderia cepacia, CDC gr.IV C-2, and Sphingomonas paucimobilis. Comparison of microbial contamination between the frequencies of disinfection showed a significantly lower number of contaminated samples when the cups were disinfected once daily than when disinfected once at intervals of 2-7 d (p=0.00037). In addition, comparison between the presence and absence of preservatives contained in the nebulization solution showed a significantly lower number of contaminated samples in the presence, rather than in the absence, of preservatives (p=0.00001). These results show that disinfection of ultrasonic nebulizers at 24-h intervals is desirable. In particular, when nebulization solutions not containing preservatives are used, disinfection at 24-h intervals is indispensable.