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The study evaluates essential oils from Ocotea diospyrifolia and Ocotea velloziana, including their combinations with polymyxin B, using chemical profiling, checkerboard assays, survival curves, and biofilm inhibition. Mechanisms are assessed via membrane permeability, reactive oxygen species, and SEM, with safety tested by hemolysis and Caenorhabditis elegans toxicity. In vivo larval infection models show improved survival with reduced PMB requirements, indicating these oils as promising antibiotic adjuvants.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":40,"@type":76,"position":81},"https://docshare.wps.com/document/research-report/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/overcoming-polymyxin-resistance-in-klebsiella-pneumoniae-with-ocotea-essential-oils-insights-from-in-vitro-and-in-vivo-analyses/443768/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/overcoming-polymyxin-resistance-in-klebsiella-pneumoniae-with-ocotea-essential-oils-insights-from-in-vitro-and-in-vivo-analyses/443768.png","ImageObject",300,407,{"name":92,"@type":93},"Damian","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-09-30","2026-09-29",true,{"@type":102,"interactionType":103,"userInteractionCount":14},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What essential oils were tested against carbapenem-polymyxin-resistant Klebsiella pneumoniae?","Question",{"text":112,"@type":113},"The study tested essential oils from Ocotea diospyrifolia (OdEO) and Ocotea velloziana (OvEO), both alone and combined with polymyxin B.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How were antimicrobial effects and synergy evaluated?",{"text":117,"@type":113},"Antimicrobial activity and synergy were assessed using checkerboard assays, survival curves, and biofilm inhibition, alongside analyses of membrane permeability, reactive oxygen species levels, and SEM.",{"name":119,"@type":110,"acceptedAnswer":120},"What outcomes were observed in the in vivo infection model?",{"text":121,"@type":113},"In C. elegans larval infection models, OdEO-PMB and OvEO-PMB improved survival rates to 72.4% and 50.9% respectively, and also reduced the polymyxin B concentration required to inhibit bacterial growth.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},443768,1790740283,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":39,"category_name":40,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":14,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":139,"language":140,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":144,"read_time":41},137451208677,"https://ap-avatar.wpscdn.com/davatar_155a257f0dc6eb9ab79c44ca47cae57d","This article is licensed under CC-BY 4.0   \n[http://pubs.acs.org/journal/acsodf](http://pubs.acs.org/journal/acsodf)  Article   \nOvercoming Polymyxin Resistance in Klebsiella pneumoniae with Ocotea Essential Oils: Insights from In Vitro and In Vivo Analyses  \nIzadora D. Faccin, Julia P. Arantes, Mariana C. Sturaro, Eduardo J. Coutinho,  \nDanielle C. da Cruz do Nascimento, Claudia A. L. Cardoso, Flavio M. Alves, Shaline S. L. Fernandes, Nathalia da S. Damacena, Gleyce H. de Almeida de Souza, Ruana C. C. da Silva, Luana Rossato, Euclésio Simionatto, and Simone Simionatto*  \n Cite This: ACS Omega 2025, 10, 58963−58974  \nRead Online  \n\n|  |  |  |  |  |  |\n| --- | --- | --- | --- | --- | --- |\n| ACCESS   | Metrics & More |  |  Article Recommendations |  | *sı Supporting Information |\n\nABSTRACT: Antimicrobial resistance, particularly in carbapenem-polymyxin-resistant Klebsiella pneumoniae (CPR-Kp), is a major challenge associated with severe infections. In this study, we assessed the chemical composition and antimicrobial properties of essential oils (EOs) from Ocotea diospyrifolia (OdEO) and Ocotea velloziana (OvEO) against CPR-Kp. The EOs were extracted from the leaves via hydrodistillation and analyzed using gas chromatography−mass spectrometry. The antimicrobial activities of the EOs, alone and along with polymyxin B (OdEO-PMB and OvEO-PMB), were assessed through checkerboard assays, survival curves, and biofilm inhibition. Cell membrane permeability, reactive oxygen  \nspecies levels, and scanning electron microscopy (SEM) were used to investigate antimicrobial mechanisms. Safety was evaluated by conducting hemolysis and toxicity tests in Caenorhabditis elegans. An in vivo infection model was constructed using C. elegans larvae to assess survival rates. OdEO and OvEO exhibited distinct chemical compositions, with α-bisabolol and viridiflorene as the major components, respectively. In silico analyses revealed that OdEO components can modulate the porin OmpK36, suggesting their ability to serve as antibiotic adjuvants. OdEO-PMB and OvEO-PMB reduced the PMB concentration required to inhibit CPR-Kp growth by 32-fold. Both combinations inhibited biofilm formation and caused bacterial death. The OdEO-PMB combination induced oxidative stress and increased protein leakage. Both treatments were nontoxic and nonhemolytic in the assay performed. In the infection models, OdEO-PMB and OvEO-PMB improved C. elegans survival rates to 72.4% and 50.9%, respectively. These results indicated that the Ocotea essential oils investigated are effective adjuvants for PMB, suggesting that they can be used to develop novel therapeutic strategies against CPR-Kp strains.  \n■ INTRODUCTION  \nAntimicrobial resistance (AMR) is a critical global health concern, contributing significantly to morbidity and mortality worldwide.1 Given this growing threat, the World Health Organization has classified carbapenem-resistant Klebsiella pneumoniae as a priority pathogen because it can develop resistance to multiple classes of antibiotics, thereby challenging and limiting clinical management.2  \nOlder classes of antibiotics, such as polymyxins, have reemerged as one of the few remaining therapeutic options for carbapenem-resistant K. pneumoniae, although their clinical application is constrained by nephrotoxicity and neurotoxicity.3−5 Additionally, the increasing prevalence of polymyxin resistance mechanisms, including remodeling of the bacterial cell membrane via chromosomal alterations, such as mutations in the mgrB gene, and the spread of plasmid-encoded mcr genes, which facilitate horizontal gene transfer between bacteria, poses a significant challenge by limiting the availability of effective  \n6−8 treatments.  \nGiven these limitations, innovative strategies need to be developed to combat AMR. One promising approach involves the application of conventional antibiotics with phytochemicals, such as essential oils (EOs), which has demonstrated a good tolerability profil","cbCaisl5l2BSpAHY","https://ap.wps.com/l/cbCaisl5l2BSpAHY","pdf",7030859,12,"English","# Abstract\n# Introduction\n# Results\n## Gas chromatography−mass spectrometry (GC−MS)","[{\"question\":\"What essential oils were tested against carbapenem-polymyxin-resistant Klebsiella pneumoniae?\",\"answer\":\"The study tested essential oils from Ocotea diospyrifolia (OdEO) and Ocotea velloziana (OvEO), both alone and combined with polymyxin B.\"},{\"question\":\"How were antimicrobial effects and synergy evaluated?\",\"answer\":\"Antimicrobial activity and synergy were assessed using checkerboard assays, survival curves, and biofilm inhibition, alongside analyses of membrane permeability, reactive oxygen species levels, and SEM.\"},{\"question\":\"What outcomes were observed in the in vivo infection model?\",\"answer\":\"In C. elegans larval infection models, OdEO-PMB and OvEO-PMB improved survival rates to 72.4% and 50.9% respectively, and also reduced the polymyxin B concentration required to inhibit bacterial growth.\"}]","Overcoming Polymyxin Resistance in Klebsiella pneumoniae with Ocotea Essential Oils - Insights from In Vitro and In Vivo Analyses | PDF",1790705296]