Pseudomonas aeruginosa investigation in water samples of Campania region, Southern Italy.

Background: Pseudomonas aeruginosa can be found in pipes and mainly affects immunocompromised patients.

Methods: From March to September 2023, 393 drinking water samples were collected and analysed from taps of 21 hospital and 26 non-hospital facilities of Campania region. Antimicrobial susceptibility test was conducted by broth microdilution method and whole genome sequencing was carried out.

Results: The bacterium was detected in 47 samples (12.0%) (26 from hospitals and 21 from non-hospital facilities). All strains were resistant to 1^st and 2^nd generation cephalosporin, ampicillin and ampicillin/sulbactam. Some strains showed resistance to 4^th generation cephalosporin cefepime, and 16 of the 47 isolates were multi drug resistant (10 from hospitals and 6 from non-hospital setting). 13 distinct sequence types (STs) have been highlighted in this study revealing a heterogeneous population. ST 309 was the most common observed genotype. It was observed the presence of the same clone in different wards of the same hospital. The presence of the same clone in different facilities indicate P. aeruginosa diffusion in different pipelines.

Conclusions: This study revealed P. aeruginosa presence in hospital and non-hospital settings, highlighting the importance of conducting environmental monitoring, especially in locations hosting vulnerable people. Routinely performing this monitoring is important to prevent infections in humans.