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The Impact of Aerators on Water Contamination by Emerging Gram-Negative Opportunists in At-Risk Hospital Departments

  • Maria Luisa Cristina (a1), Anna Maria Spagnolo (a1), Beatrice Casini (a2), Angelo Baggiani (a2), Pietro Del Giudice (a3), Silvio Brusaferro (a3), Andrea Poscia (a4), Umberto Moscato (a4), Fernanda Perdelli (a1) and Paolo Orlando (a1)...



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.


We analyzed the microbiological and chemical-physical characteristics of hot and cold water in some critical hospital departments.


Two hospitals in northern Italy.


We took 304 water samples over a 1-year period, at 3-month intervals, from taps used by healthcare personnel for handwashing, 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.


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).


These results reveal a high level of contamination of aerators by various species of gram-negative opportunists that are potentially very dangerous for immunocompromised patients and, therefore, the need to improve the management of these devices.


Corresponding author

Department of Health Sciences, University of Genoa, Via Pastore, 1-16132 Genova, Italy (


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The Impact of Aerators on Water Contamination by Emerging Gram-Negative Opportunists in At-Risk Hospital Departments

  • Maria Luisa Cristina (a1), Anna Maria Spagnolo (a1), Beatrice Casini (a2), Angelo Baggiani (a2), Pietro Del Giudice (a3), Silvio Brusaferro (a3), Andrea Poscia (a4), Umberto Moscato (a4), Fernanda Perdelli (a1) and Paolo Orlando (a1)...


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