{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T22:15:47Z","timestamp":1783462547112,"version":"3.55.0"},"reference-count":83,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2022,6,14]],"date-time":"2022-06-14T00:00:00Z","timestamp":1655164800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Pathogens"],"abstract":"<jats:p>Legionella pneumophila (Lp), responsible for a severe pneumonia called Legionnaires\u2019 disease, represents an important health burden in Europe. Prevention and control of Lp contamination in warm water systems is still a great challenge often due to the failure in disinfection procedures. The aim of this study was to evaluate the in vitro activity of Terpinen-4-ol (T-4-ol) as potential agent for Lp control, in comparison with the essential oil of Melaleuca alternifolia (tea tree) (TTO. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of T-4-ol were determined by broth micro-dilution and a micro-atmosphere diffusion method to investigate the anti-Lp effects of T-4-ol and TTO vapors. Scanning Electron Microscopy (SEM) was adopted to highlight the morphological changes and Lp damage following T-4-ol and TTO treatments. The greatest antimicrobial activity against Lp was shown by T-4-ol with a MIC range of 0.06\u20130.125% v\/v and MBC range of 0.25\u20130.5% v\/v. The TTO and T-4-ol MIC and MBC decreased with increasing temperature (36 \u00b0C to 45 \u00b1 1 \u00b0C), and temperature also significantly influenced the efficacy of TTO and T-4-ol vapors. The time-killing assay showed an exponential trend of T-4-ol bactericidal activity at 0.5% v\/v against Lp. SEM observations revealed a concentration- and temperature- dependent effect of T-4-ol and TTO on cell surface morphology with alterations. These findings suggest that T-4-ol is active against Lp and further studies may address the potential effectiveness of T-4-ol for control of water systems.<\/jats:p>","DOI":"10.3390\/pathogens11060682","type":"journal-article","created":{"date-parts":[[2022,6,15]],"date-time":"2022-06-15T01:39:54Z","timestamp":1655257194000},"page":"682","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":31,"title":["Terpinen-4-ol, the Main Bioactive Component of Tea Tree Oil, as an Innovative Antimicrobial Agent against Legionella pneumophila"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7646-1220","authenticated-orcid":false,"given":"Francesca","family":"Mondello","sequence":"first","affiliation":[{"name":"Department of Infectious Diseases, Istituto Superiore di Sanit\u00e0, Viale Regina Elena, 299, 00161 Rome, Italy"},{"name":"Societ\u00e0 Italiana per la Ricerca sugli Oli Essenziali\u2014SIROE (Italian Society for Research on Essential Oils), Viale Regina Elena, 299, 00161 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0668-4514","authenticated-orcid":false,"given":"Stefano","family":"Fontana","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Istituto Superiore di Sanit\u00e0, Viale Regina Elena, 299, 00161 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maria","family":"Scaturro","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Istituto Superiore di Sanit\u00e0, Viale Regina Elena, 299, 00161 Rome, Italy"},{"name":"ESCMID Study Group for <i>Legionella<\/i> Infections (ESGLI), 4001 Basel, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Antonietta","family":"Girolamo","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Istituto Superiore di Sanit\u00e0, Viale Regina Elena, 299, 00161 Rome, Italy"},{"name":"Societ\u00e0 Italiana per la Ricerca sugli Oli Essenziali\u2014SIROE (Italian Society for Research on Essential Oils), Viale Regina Elena, 299, 00161 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7522-7483","authenticated-orcid":false,"given":"Marisa","family":"Colone","sequence":"additional","affiliation":[{"name":"National Center for Drug Research and Evaluation, Istituto Superiore di Sanit\u00e0, Viale Regina Elena, 299, 00161 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0143-2978","authenticated-orcid":false,"given":"Annarita","family":"Stringaro","sequence":"additional","affiliation":[{"name":"Societ\u00e0 Italiana per la Ricerca sugli Oli Essenziali\u2014SIROE (Italian Society for Research on Essential Oils), Viale Regina Elena, 299, 00161 Rome, Italy"},{"name":"National Center for Drug Research and Evaluation, Istituto Superiore di Sanit\u00e0, Viale Regina Elena, 299, 00161 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2991-0855","authenticated-orcid":false,"given":"Maura Di","family":"Vito","sequence":"additional","affiliation":[{"name":"Societ\u00e0 Italiana per la Ricerca sugli Oli Essenziali\u2014SIROE (Italian Society for Research on Essential Oils), Viale Regina Elena, 299, 00161 Rome, Italy"},{"name":"Dipartimento di Scienze Biotecnologiche di Base, Cliniche Intensivologiche e Perioperatorie, Universit\u00e0 Cattolica del Sacro Cuore, Largo A. Gemelli 8, 00168 Rome, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Maria Luisa","family":"Ricci","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases, Istituto Superiore di Sanit\u00e0, Viale Regina Elena, 299, 00161 Rome, Italy"},{"name":"ESCMID Study Group for <i>Legionella<\/i> Infections (ESGLI), 4001 Basel, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2022,6,14]]},"reference":[{"key":"ref_1","unstructured":"European Centre for Disease Prevention and Control (ECDC) (2022, April 23). Legionnaires\u2019 Disease\u2014Annual Epidemiological Report for 2019. 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