{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T06:09:39Z","timestamp":1789711779832,"version":"4.0.1"},"reference-count":34,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T00:00:00Z","timestamp":1789689600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100009609","name":"Hospital Infantil de M\u00e9xico Federico G\u00f3mez","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100009609","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Pharmacol."],"abstract":"<jats:p>\n                    Multidrug-resistant (MDR)\n                    <jats:italic>Klebsiella<\/jats:italic>\n                    infections represent an increasing therapeutic challenge, underscoring the need for complementary antimicrobial strategies. Essential oils (EOs) are complex mixtures of bioactive compounds, and their antibacterial effects may not be fully explained by their predominant constituents. We compared the antibacterial activity of isolated carvacrol with that of oregano (\n                    <jats:italic>Origanum vulgare<\/jats:italic>\n                    ), summer savory (\n                    <jats:italic>Satureja hortensis<\/jats:italic>\n                    ), and thyme (\n                    <jats:italic>Thymus vulgaris<\/jats:italic>\n                    ) essential oils against MDR\n                    <jats:italic>Klebsiella<\/jats:italic>\n                    isolates and evaluated their ability to enhance conventional antibiotics. Essential oils were chemically characterized by gas chromatography\u2013mass spectrometry (GC\u2013MS). Antibacterial activity was evaluated by agar diffusion, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) assays. Interactions with ceftazidime, gentamicin, and ciprofloxacin were assessed using full checkerboard assays and fractional inhibitory concentration indices (FICIs). Toxicity was evaluated in\n                    <jats:italic>Galleria mellonella<\/jats:italic>\n                    and\n                    <jats:italic>Tenebrio molitor<\/jats:italic>\n                    larvae. GC\u2013MS identified carvacrol as the predominant constituent of oregano (71.47%) and summer savory (48.83%) oils, whereas thyme oil contained low levels of carvacrol (1.83%). Whole oregano and summer savory oils exhibited greater bactericidal activity than isolated carvacrol in several comparisons, despite the high carvacrol content of these oils. Thyme oil also showed substantial antibacterial activity despite its low carvacrol concentration, indicating that activity was not determined solely by carvacrol abundance. Toxicity assays indicated low toxicity for carvacrol, oregano, and thyme oils under the tested conditions, whereas summer savory showed moderate, species-dependent toxicity. Overall, whole essential oils exhibited antibacterial activities that could not be explained solely by their carvacrol content, supporting a contribution of their multicomponent phytochemical composition. Their ability to potentiate conventional antibiotics further supports their potential as complementary antimicrobial agents against MDR\n                    <jats:italic>Klebsiella<\/jats:italic>\n                    . Further studies using purified constituents and defined combinations are warranted to determine the specific mechanisms underlying these effects.\n                  <\/jats:p>","DOI":"10.3389\/fphar.2026.1918941","type":"journal-article","created":{"date-parts":[[2026,9,18]],"date-time":"2026-09-18T05:38:37Z","timestamp":1789709917000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Carvacrol exhibits potent anti-Klebsiella activity, whereas the multicomponent composition of essential oils may contribute to their enhanced antibacterial activity"],"prefix":"10.3389","volume":"17","author":[{"given":"Magaly Jaquelyne","family":"Lara-Garcia","sequence":"first","affiliation":[{"name":"Facultad de Ciencias de la Salud, Universidad Aut\u00f3noma de Tlaxcala","place":["Tlaxcala, Mexico"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luz Ofelia","family":"Franco-Sandoval","sequence":"additional","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Pat\u00f3genos Respiratorios, Hospital Infantil de M\u00e9xico Federico G\u00f3mez","place":["Ciudad de M\u00e9xico, Mexico"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Axel David","family":"Briones-Guzm\u00e1n","sequence":"additional","affiliation":[{"name":"Facultad de Ciencias de la Salud, Universidad Aut\u00f3noma de Tlaxcala","place":["Tlaxcala, Mexico"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mariana","family":"Romo-Castillo","sequence":"additional","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Enfermedades Infecciosas y Parasitarias, Hospital Infantil de M\u00e9xico Federico G\u00f3mez","place":["Ciudad de M\u00e9xico, Mexico"]},{"name":"Investigadores por M\u00e9xico SECIHTI, Secretar\u00eda de Ciencia, Humanidades, Tecnolog\u00eda e Innovaci\u00f3n","place":["Ciudad de M\u00e9xico, Mexico"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,9,18]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"1534","DOI":"10.3390\/nu18101534","article-title":"A review of the properties of clinically evaluated plant-derived agents in the treatment of respiratory infections","volume":"18","author":"Alexandrova","year":"2026","journal-title":"Nutrients"},{"key":"B2","doi-asserted-by":"publisher","first-page":"55","DOI":"10.1186\/s12866-023-02797-x","article-title":"Antibacterial and anti-biofilm properties of carvacrol alone and in combination with cefixime against Escherichia coli","volume":"23","author":"Asadi","year":"2023","journal-title":"BMC Microbiol."},{"key":"B3","doi-asserted-by":"publisher","first-page":"100333","DOI":"10.1016\/j.microb.2025.100333","article-title":"Klebsiella Pneumoniae: a growing threat in the era of antimicrobial resistance","volume":"7","author":"Asokan","year":"2025","journal-title":"Microbe"},{"key":"B4","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1080\/23744235.2026.2672635","article-title":"A comparative analysis of pediatric Klebsiella oxytoca and Klebsiella pneumoniae bacteremia: clinical characteristics, antimicrobial susceptibility, and outcomes","volume":"58","author":"Atay \u00dcnal","year":"2026","journal-title":"Infect. 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