{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T04:10:38Z","timestamp":1778213438908,"version":"3.51.4"},"reference-count":25,"publisher":"Springer Science and Business Media LLC","issue":"1","license":[{"start":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T00:00:00Z","timestamp":1778198400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"},{"start":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T00:00:00Z","timestamp":1778198400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0"}],"funder":[{"DOI":"10.13039\/100020098","name":"Innovative Health Initiative","doi-asserted-by":"publisher","award":["853989"],"award-info":[{"award-number":["853989"]}],"id":[{"id":"10.13039\/100020098","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Tres Cantos Open Lab Foundation","award":["TC281"],"award-info":[{"award-number":["TC281"]}]}],"content-domain":{"domain":["link.springer.com"],"crossmark-restriction":false},"short-container-title":["Infect Dis Poverty"],"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>\n                    Buruli ulcer (BU), a neglected tropical disease caused by\n                    <jats:italic>Mycobacterium ulcerans<\/jats:italic>\n                    (\n                    <jats:italic>Mul<\/jats:italic>\n                    ), is treated with an 8-week regimen of rifampicin (RIF) and clarithromycin (CLA). Clinical trials are currently evaluating amoxicillin\/clavulanate (AMX\/CLV) co-administration to reduce treatment duration. However, conventional methods for assessing in vitro drug efficacy against\n                    <jats:italic>Mul<\/jats:italic>\n                    , like colony-forming units (CFUs), are slow and cumbersome. The ribosomal RNA synthesis ratio (RS-ratio) measures ribosome biogenesis and serves as a proxy of metabolic activity. While it is a promising predictive biomarker for treatment shortening in tuberculosis, its application in\n                    <jats:italic>Mul<\/jats:italic>\n                    remains unexplored. Here, we evaluated the RS-ratio for\n                    <jats:italic>Mul<\/jats:italic>\n                    drug activity assessment through RNA extractions from time-kill assays using RIF, CLA, and AMX\/CLV, alone or in combinations. RIF\u2009+\u2009AMX\/CLV-containing combinations produced a potent, rapid RS-ratio reduction, decreasing from a baseline of \u22482000 to \u2248200 as early as day 3, and reaching their maximal inhibition (\u224850\u201360) between days 7 and 10. Notably, this metabolic decline preceded the CFUs and luminescence drops observed in prior studies. Interestingly, the RS-ratio detected a metabolic recovery between days 14 and 28 (\u2248400), suggesting remaining bacterial viability, a phenomenon not observed by CFUs or luminescence. In summary, this is the first report using the RS-ratio to evaluate antibiotic activity against\n                    <jats:italic>Mul<\/jats:italic>\n                    . Our findings validate the RS-ratio as a molecular tool for assessing the sterilizing potential of new regimens to inform future research and clinical trial designs for the treatment of BU. Our results support the RIF\u2009+\u2009CLA\u2009+\u2009AMX\/CLV regimen selection for BU treatment shortening in the BLMs4BU clinical trials (NCT05169554, PACTR202209521256638).\n                  <\/jats:p>\n                  <jats:p>\n                    <jats:bold>Graphical Abstract<\/jats:bold>\n                  <\/jats:p>","DOI":"10.1186\/s40249-026-01449-2","type":"journal-article","created":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T03:22:15Z","timestamp":1778210535000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["The ribosomal RNA synthesis ratio biomarker in Mycobacterium ulcerans for drug activity evaluation"],"prefix":"10.1186","volume":"15","author":[{"given":"Juan","family":"Calvet-Seral","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Emma","family":"S\u00e1ez-L\u00f3pez","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Patricio R.","family":"L\u00f3pez-Exp\u00f3sito","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Santiago","family":"Ferrer-Bazaga","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Juan Jos\u00e9","family":"Vaquero","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Santiago","family":"Ram\u00f3n-Garc\u00eda","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alfonso","family":"Mendoza-Losana","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"297","published-online":{"date-parts":[[2026,5,8]]},"reference":[{"key":"1449_CR1","volume-title":"Buruli ulcer in Africa: 20 years of progress","author":"World Health Organization","year":"2025","unstructured":"World Health Organization. Buruli ulcer in Africa: 20 years of progress. Brazzaville: WHO Regional Office for Africa; 2025. https:\/\/www.afro.who.int\/publications\/buruli-ulcer-africa-20-years-progress"},{"key":"1449_CR2","volume-title":"Ending the neglect to attain the Sustainable Development Goals: a road map for neglected tropical diseases 2021\u20132030","author":"World Health Organization","year":"2020","unstructured":"World Health Organization. Ending the neglect to attain the Sustainable Development Goals: a road map for neglected\ntropical diseases 2021\u20132030. Geneva: World Health Organization; 2020. https:\/\/www.who.int\/publications\/i\/item\/9789240010352"},{"key":"1449_CR3","doi-asserted-by":"publisher","first-page":"e0007126","DOI":"10.1371\/journal.pntd.0007126","volume":"13","author":"MP Arenaz-Callao","year":"2019","unstructured":"Arenaz-Callao MP, Gonz\u00e1lez Del R\u00edo R, Luc\u00eda Quintana A, Thompson CJ, Mendoza-Losana A, Ram\u00f3n-Garc\u00eda S. Triple oral beta-lactam containing therapy for Buruli ulcer treatment shortening. PLoS Negl Trop Dis. 2019;13:e0007126. https:\/\/doi.org\/10.1371\/journal.pntd.0007126.","journal-title":"PLoS Negl Trop Dis"},{"key":"1449_CR4","doi-asserted-by":"publisher","first-page":"e0011867","DOI":"10.1371\/journal.pntd.0011867","volume":"18","author":"E S\u00e1ez-L\u00f3pez","year":"2024","unstructured":"S\u00e1ez-L\u00f3pez E, Mill\u00e1n-Placer AC, Luc\u00eda A, Ram\u00f3n-Garc\u00eda S. Amoxicillin\/clavulanate in combination with rifampicin\/clarithromycin is bactericidal against Mycobacterium ulcerans. PLoS Negl Trop Dis. 2024;18:e0011867. https:\/\/doi.org\/10.1371\/journal.pntd.0011867.","journal-title":"PLoS Negl Trop Dis"},{"key":"1449_CR5","doi-asserted-by":"publisher","first-page":"559","DOI":"10.1186\/s13063-022-06473-9","volume":"23","author":"RC Johnson","year":"2022","unstructured":"Johnson RC, S\u00e1ez-L\u00f3pez E, Anagonou ES, Kpoton GG, Ayelo AG, Gnimavo RS, et al. Comparison of 8 weeks standard treatment (rifampicin plus clarithromycin) vs. 4 weeks standard plus amoxicillin\/clavulanate treatment [RC8 vs. RCA4] to shorten Buruli ulcer disease therapy (the BLMs4BU trial): Study protocol for a randomized controlled multi-centre trial in Benin. Trials. 2022;23:559. https:\/\/doi.org\/10.1186\/s13063-022-06473-9.","journal-title":"Trials"},{"key":"1449_CR6","unstructured":"BLMs4BU Project | Reducing Treatment of Buruli Ulcer. https:\/\/blms4bu.org\/. Accessed 6 May 2025."},{"key":"1449_CR7","doi-asserted-by":"publisher","first-page":"2899","DOI":"10.1038\/s41467-021-22833-6","volume":"12","author":"ND Walter","year":"2021","unstructured":"Walter ND, Born SEM, Robertson GT, Reichlen M, Dide-Agossou C, Ektnitphong VA, et al. Mycobacterium tuberculosis precursor rRNA as a measure of treatment-shortening activity of drugs and regimens. Nat Commun. 2021;12:2899. https:\/\/doi.org\/10.1038\/s41467-021-22833-6.","journal-title":"Nat Commun"},{"key":"1449_CR8","doi-asserted-by":"publisher","first-page":"e1756","DOI":"10.1371\/journal.pntd.0001756","volume":"6","author":"M Beissner","year":"2012","unstructured":"Beissner M, Symank D, Phillips RO, Amoako YA, Awua-Boateng N-Y, Sarfo FS, et al. Detection of viable Mycobacterium ulcerans in clinical samples by a novel combined 16S rRNA reverse transcriptase\/IS2404 real-time qPCR assay. PLoS Negl Trop Dis. 2012;6:e1756. https:\/\/doi.org\/10.1371\/journal.pntd.0001756.","journal-title":"PLoS Negl Trop Dis"},{"key":"1449_CR9","doi-asserted-by":"publisher","first-page":"1006","DOI":"10.1164\/arrd.1973.107.6.1006","volume":"107","author":"K Konno","year":"1973","unstructured":"Konno K, Oizumi K, Oka S. Mode of action of rifampin on mycobacteria. II. Biosynthetic studies on the inhibition of ribonucleic acid polymerase of Mycobacterium bovis BCG by rifampin and uptake of rifampin- 14 C by Mycobacterium phlei. Am Rev Respir Dis. 1973;107:1006\u201312. https:\/\/doi.org\/10.1164\/arrd.1973.107.6.1006.","journal-title":"Am Rev Respir Dis"},{"key":"1449_CR10","doi-asserted-by":"publisher","first-page":"737","DOI":"10.1128\/jb.108.2.737-741.1971","volume":"108","author":"RJ White","year":"1971","unstructured":"White RJ, Lancini GC, Silvestri LG. Mechanism of action of rifampin on Mycobacterium smegmatis. J Bacteriol. 1971;108:737\u201341. https:\/\/doi.org\/10.1128\/jb.108.2.737-741.1971.","journal-title":"J Bacteriol"},{"key":"1449_CR11","doi-asserted-by":"publisher","first-page":"414","DOI":"10.1128\/AAC.37.3.414","volume":"37","author":"N Honore","year":"1993","unstructured":"Honore N, Cole ST. Molecular basis of rifampin resistance in Mycobacterium leprae. Antimicrob Agents Chemother. 1993;37:414\u20138. https:\/\/doi.org\/10.1128\/AAC.37.3.414.","journal-title":"Antimicrob Agents Chemother"},{"key":"1449_CR12","doi-asserted-by":"publisher","first-page":"e0148322","DOI":"10.1128\/aac.01483-22","volume":"67","author":"MJ Reichlen","year":"2023","unstructured":"Reichlen MJ, Born SEM, Lyons MA, Rossmassler K, Reid J, Robertson GT, et al. Standardized RS ratio metrics to assess tuberculosis antimicrobial efficacy and potency. Antimicrob Agents Chemother. 2023;67:e0148322. https:\/\/doi.org\/10.1128\/aac.01483-22.","journal-title":"Antimicrob Agents Chemother"},{"key":"1449_CR13","doi-asserted-by":"publisher","first-page":"613","DOI":"10.4065\/74.6.613","volume":"74","author":"S Alvarez-Elcoro","year":"1999","unstructured":"Alvarez-Elcoro S, Enzler MJ. The macrolides: erythromycin, clarithromycin, and azithromycin. Mayo Clin Proc. 1999;74:613\u201334. https:\/\/doi.org\/10.4065\/74.6.613.","journal-title":"Mayo Clin Proc"},{"key":"1449_CR14","first-page":"1","volume-title":"xPharm: the comprehensive pharmacology reference","author":"SS Castle","year":"2007","unstructured":"Castle SS. Amoxicillin. In: Enna SJ, Bylund DB, editors. xPharm: the comprehensive pharmacology reference. Amsterdam: Elsevier; 2007. p. 1\u20136."},{"key":"1449_CR15","doi-asserted-by":"publisher","first-page":"810","DOI":"10.4269\/ajtmh.16-0478","volume":"97","author":"SK Gupta","year":"2017","unstructured":"Gupta SK, Drancourt M, Rolain J-M. In silico prediction of antibiotic resistance in Mycobacterium ulcerans Agy99 through whole genome sequence analysis. Am J Trop Med Hyg. 2017;97:810\u20134. https:\/\/doi.org\/10.4269\/ajtmh.16-0478.","journal-title":"Am J Trop Med Hyg"},{"key":"1449_CR16","doi-asserted-by":"publisher","first-page":"101213","DOI":"10.1016\/j.drup.2025.101213","volume":"80","author":"S Ram\u00f3n-Garc\u00eda","year":"2025","unstructured":"Ram\u00f3n-Garc\u00eda S, Gonz\u00e1lez Del R\u00edo R, Arenaz-Callao MP, Boshoff HI, Rullas J, Anca S, et al. Sanfetrinem, an oral \u03b2-lactam antibiotic repurposed for the treatment of tuberculosis. Drug Resist Updat. 2025;80:101213. https:\/\/doi.org\/10.1016\/j.drup.2025.101213.","journal-title":"Drug Resist Updat"},{"key":"1449_CR17","doi-asserted-by":"publisher","first-page":"305","DOI":"10.1016\/j.diagmicrobio.2018.06.015","volume":"92","author":"ELM Schoutrop","year":"2018","unstructured":"Schoutrop ELM, Brouwer MAE, Jenniskens JCA, Ferro BE, Mouton JW, Aarnoutse RE, et al. The stability of antimycobacterial drugs in media used for drug susceptibility testing. Diagn Microbiol Infect Dis. 2018;92:305\u20138. https:\/\/doi.org\/10.1016\/j.diagmicrobio.2018.06.015.","journal-title":"Diagn Microbiol Infect Dis"},{"key":"1449_CR18","doi-asserted-by":"publisher","first-page":"784","DOI":"10.1128\/JCM.01951-10","volume":"49","author":"X Yu","year":"2011","unstructured":"Yu X, Jiang G, Li H, Zhao Y, Zhang H, Zhao L, et al. Rifampin stability in 7H9 broth and L\u00f6wenstein-Jensen medium. J Clin Microbiol. 2011;49:784\u20139. https:\/\/doi.org\/10.1128\/JCM.01951-10.","journal-title":"J Clin Microbiol"},{"key":"1449_CR19","doi-asserted-by":"publisher","first-page":"34293","DOI":"10.1038\/srep34293","volume":"6","author":"S Ram\u00f3n-Garc\u00eda","year":"2016","unstructured":"Ram\u00f3n-Garc\u00eda S, Gonz\u00e1lez Del R\u00edo R, Villarejo AS, Sweet GD, Cunningham F, Barros D, et al. Repurposing clinically approved cephalosporins for tuberculosis therapy. Sci Rep. 2016;6:34293. https:\/\/doi.org\/10.1038\/srep34293.","journal-title":"Sci Rep"},{"key":"1449_CR20","doi-asserted-by":"publisher","first-page":"296","DOI":"10.1302\/2046-3758.65.BJR-2017-0276.R1","volume":"6","author":"E Samara","year":"2017","unstructured":"Samara E, Moriarty TF, Decosterd LA, Richards RG, Gautier E, Wahl P. Antibiotic stability over six weeks in aqueous solution at body temperature with and without heat treatment that mimics the curing of bone cement. Bone Joint Res. 2017;6:296\u2013306. https:\/\/doi.org\/10.1302\/2046-3758.65.BJR-2017-0276.R1.","journal-title":"Bone Joint Res"},{"key":"1449_CR21","doi-asserted-by":"publisher","first-page":"5","DOI":"10.1093\/jac\/39.1.5","volume":"39","author":"PO Erah","year":"1997","unstructured":"Erah PO, Goddard AF, Barrett DA, Shaw PN, Spiller RC. The stability of amoxycillin, clarithromycin and metronidazole in gastric juice: relevance to the treatment of Helicobacter pylori infection. J Antimicrob Chemother. 1997;39:5\u201312. https:\/\/doi.org\/10.1093\/jac\/39.1.5.","journal-title":"J Antimicrob Chemother"},{"key":"1449_CR22","doi-asserted-by":"publisher","first-page":"1321","DOI":"10.1128\/jcm.34.5.1321-1322.1996","volume":"34","author":"TD Moore","year":"1996","unstructured":"Moore TD, Horton R, Utrup LJ, Miller LA, Poupard JA. Stability of amoxicillin-clavulanate in BACTEC medium determined by high-performance liquid chromatography and bioassay. J Clin Microbiol. 1996;34:1321\u20132. https:\/\/doi.org\/10.1128\/jcm.34.5.1321-1322.1996.","journal-title":"J Clin Microbiol"},{"key":"1449_CR23","doi-asserted-by":"publisher","first-page":"2051","DOI":"10.3389\/fmicb.2016.02051","volume":"7","author":"EA Lallemand","year":"2016","unstructured":"Lallemand EA, Lacroix MZ, Toutain P-L, Boullier S, Ferran AA, Bousquet-Melou A. In vitro degradation of antimicrobials during use of broth microdilution method can increase the measured minimal inhibitory and minimal bactericidal concentrations. Front Microbiol. 2016;7:2051. https:\/\/doi.org\/10.3389\/fmicb.2016.02051.","journal-title":"Front Microbiol"},{"issue":"Suppl 1","key":"1449_CR24","doi-asserted-by":"publisher","first-page":"S1","DOI":"10.1093\/cid\/civ484","volume":"61","author":"M Cavaleri","year":"2015","unstructured":"Cavaleri M, Manolis E. Hollow fiber system model for tuberculosis: the European Medicines Agency experience. Clin Infect Dis. 2015;61(Suppl 1):S1-4. https:\/\/doi.org\/10.1093\/cid\/civ484.","journal-title":"Clin Infect Dis"},{"key":"1449_CR25","doi-asserted-by":"publisher","first-page":"1711","DOI":"10.1111\/bcp.16068","volume":"90","author":"DA Aguilar-Ayala","year":"2024","unstructured":"Aguilar-Ayala DA, Sanz-Garc\u00eda F, Rabodoarivelo MS, Susanto BO, Bailo R, Eveque-Mourroux MR, et al. Evaluation of critical parameters in the hollow-fibre system for tuberculosis: a case study of moxifloxacin. Br J Clin Pharmacol. 2024;90:1711\u201327. https:\/\/doi.org\/10.1111\/bcp.16068.","journal-title":"Br J Clin Pharmacol"}],"container-title":["Infectious Diseases of Poverty"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/link.springer.com\/content\/pdf\/10.1186\/s40249-026-01449-2.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/link.springer.com\/article\/10.1186\/s40249-026-01449-2","content-type":"text\/html","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/link.springer.com\/content\/pdf\/10.1186\/s40249-026-01449-2.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T03:22:19Z","timestamp":1778210539000},"score":1,"resource":{"primary":{"URL":"https:\/\/link.springer.com\/10.1186\/s40249-026-01449-2"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,5,8]]},"references-count":25,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2026,12]]}},"alternative-id":["1449"],"URL":"https:\/\/doi.org\/10.1186\/s40249-026-01449-2","relation":{},"ISSN":["2049-9957"],"issn-type":[{"value":"2049-9957","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,8]]},"assertion":[{"value":"11 December 2025","order":1,"name":"received","label":"Received","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"21 April 2026","order":2,"name":"accepted","label":"Accepted","group":{"name":"ArticleHistory","label":"Article History"}},{"value":"8 May 2026","order":3,"name":"first_online","label":"First Online","group":{"name":"ArticleHistory","label":"Article History"}},{"order":1,"name":"Ethics","group":{"name":"EthicsHeading","label":"Declarations"}},{"value":"The authors declare no competing interests.","order":2,"name":"Ethics","group":{"name":"EthicsHeading","label":"Competing interests"}}],"article-number":"51"}}