Effectiveness of water system chemical disinfection against Pseudomonas aeruginosa infections, despite a not-so obvious connection.

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.