Determinants of Legionella spp. presence in hospital water surveillance: a five-year, three-centre study from Greece.

Authors

Maria Athanasiou, Athanasia Palaiologou, Ioanna Chatziprodromidou, Joanna Velissari, Apostolos Vantarakis

Published in

The Journal of hospital infection. Sep 09, 2026. Epub Sep 09, 2026.

Abstract

Hospital water systems are persistent reservoirs of Legionella spp. and a recognised threat to immunocompromised inpatients.
To characterise the burden and factors associated with Legionella spp. contamination across three Greek hospitals over five years METHODS: We retrospectively analysed 292 water samples from three acute-care Greek hospitals (March 2020-April 2025), cultured by a single accredited laboratory using the methods defined in ISO 11731:2017. A sample was classified as positive when viable Legionella spp. were recovered at or above the laboratory limit of detection; records reported as zero counts or below the limit of detection were treated as non-detections.
Overall, 20.9% (61/292) of samples were positive, with marked between-hospital differences: 21.2%, 35.0% and 4.4% (χ²=27.1, p<10^-6). Hospital 2 carried the heaviest burden (mean 2188 CFU/L; 9.7% >10 000 CFU/L) and produced nine of the ten highest readings, from hot-water taps. After adjustment, between-hospital differences remained the factor most strongly associated with detection (Hospital 2 vs 3: OR=15.0, 95% CI 4.8-46.4; Hospital 1 vs 3: OR=8.6, 95% CI 2.0-38.0; both p<0.01). Hot-water sampling was independently associated with detection (OR=2.76, 95% CI 1.36-5.59, p=0.005).
Differences between these three hospitals, together with hot-water systems, were the factors most strongly associated with Legionella spp. Persistent contamination in two of three networks supports a shift from outlet-level reactive disinfection towards whole-system, risk-based water-safety planning aligned with World Health Organization (WHO) and European Study Group for Legionella Infections (ESGLI) guidance. As a three-hospital retrospective study, these findings are preliminary and require confirmation in larger datasets.

PMID:
42716439
Bibliographic data and abstract were imported from PubMed on 10 Sep 2026.

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