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Effectiveness of water system chemical disinfection against Pseudomonas aeruginosa infections, despite a not-so obvious connection
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International audience. Background: Pseudomonas aeruginosa is a well-recognized opportunistic pathogen frequently responsible for hospital-acquired infections. Acquisition routes of P. aeruginosa are both endogenous and exogenous, including transmission from portion of the hospital water system.Methods: Impact of disinfection procedures of the water system and description routes of P. aeruginosa transmission in a surgical ICU over a two-year period were investigated. Two distinct periods A and B were considered, respectively before and after the disinfection. Fourier transform infrared spectroscopy was used to compare isolates recovered from patients and tap water.Results: Overall, 21.3% tap water samples were positive but with a significantly lower rate in the period B (p< 0.01). Concomitantly, the prevalence of patients positive for P. aeruginosa decreased from 2.6% to 1% (p< 0.01), suggesting a correlation between the presence of environmental sources and patient contaminations. Results revealed that 18% of patients were involved in cross-transmission events not related with any isolate recovered from water, suggesting transmission through care practices. Conversely, only one environmental transmission event was suspected in a patient.Conclusion: Although the link between the hospital environment and patients was unclear, HCW-associated care practices could be related to contaminated point of use waters and then indirect spreading to patients.