One Health in hospital settings: the role of water as an invisible reservoir of opportunistic pathogens.

OBJECTIVES: To evaluate the microbiological quality of a hospital's treated water distribution system, characterize opportunistic bacterial isolates and their antimicrobial susceptibility profiles, investigate the genetic relatedness between environmental and clinical isolates from a One Health perspective. STUDY DESIGN: Prospective observational study. METHODS: A total of 352 water samples were collected over six months from strategic locations within a public teaching hospital. Samples were analyzed for total coliforms, Escherichia coli, heterotrophic bacteria (HB), bacterial isolation and identification, antimicrobial susceptibility testing, and ERIC-PCR genotyping was applied to Pseudomonas aeruginosa isolates to analyse their similarity with clinical isolates. Statistical analysis used the chi-square test of independence (χ2). RESULTS: Despite legal compliance for coliforms, elevated HB counts were found in 17% of water tank samples and 12% of ICU samples. Pathogens such as Pseudomonas aeruginosa, Stenotrophomonas maltophilia, and Enterobacter spp. were isolated. Enterobacter spp. isolates exhibited resistance to multiple β-lactams. Genotypic analysis did not reveal a direct clonal relationship between P. aeruginosa isolates from water and NDM-producing P. aeruginosa isolates recovered from hospitalized patients. CONCLUSIONS: Although the hospital water distribution system complied with current microbiological potability standards, opportunistic bacteria were detected in localized areas of the network. The absence of clonal relatedness between environmental and clinical P. aeruginosa isolates suggests that the water system was not an active source of dissemination during the study period. These findings support the value of routine environmental surveillance as part of infection prevention strategies within a One Health framework.