Our aim was to evaluate the impact of aerators on water microbiological contamination in at-risk hospital departments, with a view to quantifying the possible risk of patient exposure to waterborne microorganisms. DESIGN. Weanalyzedthemicrobiologicalandchemical-physicalcharacteristicsofhotandcoldwaterinsomecriticalhospitaldepartments. SETTING. Two hospitals in northern Italy. METHODS. Wetook304watersamplesovera1-yearperiod,at3-monthintervals,fromtapsusedbyhealthcarepersonnelforhandwashing, surgical washing, and the washing of medical equipment. We analyzed heterotrophic plate counts (HPCs) at 36°C and 22°C, nonfastidious gram-negative bacteria (GNB-NE), and Legionella pneumophila. RESULTS. The percentages of positivity and mean values of HPCs at 22 °C, HPCs at 36°C, and GNB-NE loads were significantly higher at outlet points than in the plumbing system. In particular, GNB-NE positivity was higher at outlet points than in the plumbing system in both the cold water (31.58% vs 6.58% of samples were positive) and hot water (21.05% vs 3.95%) supplies. Our results also revealed contamination by L. pneumophila both in the plumbing system and at outlet points, with percentages of positive samples varying according to the serogroup examined (serogroups 1 and 2-14). The mean concentrations displayed statistically significant (P <.001) differences between the outlet points (27,382.89 ± 42,245.33 colony-forming units [cfu]/L) and the plumbing system (19,461.84 ± 29,982.11 cfu/ L). CONCLUSIONS. These results reveal a highlevelof contamination ofaeratorsbyvariousspeciesofgram-negativeopportuniststhatare potentially very dangerous for immunocompromised patients and, therefore, the need to improve the management of these devices.
