Evaluation of Legionella Air Contamination in Healthcare Facilities by Different Sampling Methods: An Italian Multicenter Study

Healthcare facilities (HF) represent an at-risk environment for legionellosis transmission occurring after inhalation of contaminated aerosols. In general, the control of water is preferred to that of air because, to date, there are no standardized sampling protocols. air contamination was investigated in the bathrooms of 11 HF by active sampling (Surface Air System and Coriolis μ) and passive sampling using settling plates. During the 8-hour sampling, hot tap water was sampled three times. All air samples were evaluated using culture-based methods, whereas liquid samples collected using the Coriolis μ were also analyzed by real-time PCR. presence in the air and water was then compared by sequence-based typing (SBT) methods. Air contamination was found in four HF (36.4%) by at least one of the culturable methods. The culturable investigation by Coriolis μ did not yield in any enrolled HF. However, molecular investigation using Coriolis μ resulted in eight HF testing positive for in the air. Comparison of air and water contamination indicated that water concentration could be predictive of its presence in the air. Furthermore, a molecular study of 12 strains confirmed a match between the strains from air and water samples by SBT for three out of four HF that tested positive for by at least one of the culturable methods. Overall, our study shows that air detection cannot replace water sampling because the absence of microorganisms from the air does not necessarily represent their absence from water; nevertheless, air sampling may provide useful information for risk assessment. The liquid impingement technique appears to have the greatest capacity for collecting airborne if combined with molecular investigations.