Prevalence and survival of microbial contaminants in heated nebulizers

Over a 2-year period, 600 cultures of fluid in heated nebulizers in use by patients in the Peter Bent Brigham Hospital were performed. The most commonly isolated microorganisms were Pseudomonas and Alcaligenes species. Pseudomonas aeruginosa was never isolated. Three types of heated nebulizers were in use, and their contamination rate was significantly different (45 percent, 21 percent, and 8 percent, respectively; p less than 0.001). In the course of the study, the overall contamination rate decreased from 47 percent to 10 percent. This was mainly due to elmination of the type of heated nebulizer that was most prone to contamination. Five types of currently available large-reservoir nebulizers were inculated with various organisms and growth patterns studied. The various nebulizing equiment differed in its ability to inhibit or eliminate microbial growth; 1 of the heated nebulizers appeared to enhance growth of some of the inoculated bacteria.