Point-of-use water filtration reduces endemic Pseudomonas aeruginosa infections on a surgical intensive care unit

Background: Endemic infections because of Pseudomonas aeruginosa were observed on a surgical intensive care unit (ICU) for a period of >24 months. Tap water probing revealed persistent colonization of all ICU water taps with a single P aeruginosa clonotype. Methods: Water outlets of the ICU were equipped with disposable point-of-use water filters, changed in weekly and, later, 2-week intervals. To delineate the effect of the filters, 4 study approaches were followed: (1) a descriptive analysis of the incidence of P aeruginosa colonizations and infections, (2) microbiologic examinations of tap water before and after installation of the filters, (3) a comparative cohort analysis of representative patient samples from the prefilter and postfilter time periods, and (4) an analysis of general ward variables for the 2 periods. Results: (1) The mean monthly rate (+/- SD) of P aeruginosa infection/colonization episodes was 3.9 +/- 2.4 in the prefilter and 0.8 +/- 0.8 in the postfilter period. P aeruginosa colonizations were reduced by 85% (P < .0001) and invasive infections by 56% (P < .0003) in the postfilter period. (2) Microbiologic examinations of tap water revealed growth of P aeruginosa in 113 of 117 (97%) samples collected during the prefilter period, compared with 0 of 52 samples taken from filter-equipped taps. (3) In the comparative cohort analysis, a number of patient-related variables were significantly associated with P aeruginosa colonization/infection. Considering these variables in a multivariate analysis, belonging to the postfilter cohort was the factor most strongly associated with a reduced risk of P aeruginosa positivity (relative risk, 0.04; P = .0002). (4) General ward variables such as bed occupancy, personnel-to-patient ratio, or microbiologic culturing density did not differ significantly between the 2 periods. Conclusion: Taking into account various patient-related and general ward variables, point-of-use water filtration was associated with a significant reduction of chronically endemic P aeruginosa colonizations/infections on a surgical ICU.