{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,21]],"date-time":"2026-10-21T19:28:34Z","timestamp":1792610914386,"version":"4.5.0"},"reference-count":34,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2024,12,6]],"date-time":"2024-12-06T00:00:00Z","timestamp":1733443200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Basic Science Research Program through the National Research Foundation of Korea (NRF)","award":["2022R1F1A1074456"],"award-info":[{"award-number":["2022R1F1A1074456"]}]},{"DOI":"10.13039\/501100003725","name":"Ministry of Education","doi-asserted-by":"publisher","award":["2022R1F1A1074456"],"award-info":[{"award-number":["2022R1F1A1074456"]}],"id":[{"id":"10.13039\/501100003725","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Microorganisms"],"abstract":"<jats:p>The widespread resistance of enterococci to many commonly used antimicrobial agents is a growing concern. Given that the current treatment options for enterococcal infections are limited, the discovery of new therapies, including combination therapies, is necessary. We evaluated double-drug combinations of lefamulin with doxycycline, rifampin, and quinupristin\/dalfopristin for in vitro synergy against strains of Enterococcus faecium (E. faecium) and Enterococcus faecalis (E. faecalis) by using checkerboard and time-kill assays. In the checkerboard assay, the synergistic effect of lefamulin with doxycycline and rifampin was observed in 29 (85.3%) and 33 (97.1%) of the 34 different E. faecium strains tested, respectively. These combinations also showed synergistic effects against 17 (94.4%) of the 18 different vancomycin-resistant E. faecium strains. Among the 33 different E. faecalis strains, the combination of lefamulin with doxycycline, quinupristin\/dalfopristin, and rifampin displayed synergistic effects in 31 (93.9%), 26 (78.8%), and 20 (60.6%) strains, respectively. No antagonism was observed in any of the combinations. The time-kill assay confirmed the synergistic effects of all these combinations. These synergistic combinations exhibited bacteriostatic activity. Although lefamulin is not currently used to treat enterococcal infections, we suggest that these combinations may serve as alternative drug regimens.<\/jats:p>","DOI":"10.3390\/microorganisms12122515","type":"journal-article","created":{"date-parts":[[2024,12,6]],"date-time":"2024-12-06T03:44:47Z","timestamp":1733456687000},"page":"2515","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["In Vitro Synergistic Effect of Lefamulin with Doxycycline, Rifampin, and Quinupristin\/Dalfopristin Against Enterococci"],"prefix":"10.3390","volume":"12","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2167-2765","authenticated-orcid":false,"given":"Yu-Hong","family":"Min","sequence":"first","affiliation":[{"name":"College of K-Bio Health, Daegu Haany University, Gyeongsan 38610, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6115-7533","authenticated-orcid":false,"given":"Yong-ung","family":"Kim","sequence":"additional","affiliation":[{"name":"Department of Pharmaceutical Engineering, Daegu Haany University, Gyeongsan 38610, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Min Chul","family":"Park","sequence":"additional","affiliation":[{"name":"College of Pharmacy and Inje Institute of Pharmaceutical Sciences and Research, Inje University, Gimhae 50832, Republic of Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,12,6]]},"reference":[{"key":"ref_1","unstructured":"Gilmore, M.S., Clewell, D.B., Ike, Y., and Shankar, N. (2014). Enterococcal disease, epidemiology, and implications for treatment. Enterococci: From Commensals to Leading Causes of Drug Resistant Infection, Massachusetts Eye and Ear Infirmary."},{"key":"ref_2","unstructured":"Gilmore, M.S., Clewell, D.B., Ike, Y., and Shankar, N. (2014). Enterococcal infection\u2014Treatment and antibiotic resistance. Enterococci: From Commensals to Leading Causes of Drug Resistant Infection, Massachusetts Eye and Ear Infirmary."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"421","DOI":"10.4161\/viru.21282","article-title":"Intrinsic and acquired resistance mechanism in enterococcus","volume":"3","author":"Hollenbeck","year":"2012","journal-title":"Virulence"},{"key":"ref_4","unstructured":"Clinical and Laboratory Standards Institute (2020). CLSI M100: Performance Standards for Antimicrobial Susceptibility Testing, Clinical and Laboratory Standards Institute. [30th ed.]."},{"key":"ref_5","unstructured":"WHO (2017). Global Priority List of Antibiotic-Resistant Bacteria to Guide Research, Discovery, and Development of New Antibiotics, World Health Organization."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"935","DOI":"10.1002\/phar.2166","article-title":"Lefamulin: Review of a promising novel pleuromutilin antibiotic","volume":"38","author":"Veve","year":"2018","journal-title":"Pharmacother. J. Hum. Pharmacol. Drug. Ther."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"659","DOI":"10.1038\/nbt.1549","article-title":"Synergistic drug combinations tend to improve therapeutically relevant selectivity","volume":"27","author":"Krueger","year":"2009","journal-title":"Nat. Biotechnol."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/j.mib.2015.05.008","article-title":"Antimicrobial interactions: Mechanisms and implications for drug discovery and resistance evolution","volume":"27","author":"Bollenbach","year":"2015","journal-title":"Curr. Opin. Microbiol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"14918","DOI":"10.1073\/pnas.0800944105","article-title":"Drug interactions modulate the potential for evolution of resistance","volume":"105","author":"Michel","year":"2008","journal-title":"Proc. Natl. Acad. Sci. USA"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"262ra156","DOI":"10.1126\/scitranslmed.3009940","article-title":"Prediction of resistance development against drug combinations by collateral responses to component drugs","volume":"6","author":"Munck","year":"2014","journal-title":"Sci. Transl. Med."},{"key":"ref_11","first-page":"720","article-title":"In vitro interaction of lefamulin, a pleuromutilin antibiotic, and doxycycline against linezolid-and vancomycin-resistant Enterococcus faecium","volume":"70","author":"Davis","year":"2022","journal-title":"J. Investig. Med."},{"key":"ref_12","unstructured":"Paukner, S., Stoneburner, A., Ivezic-Schoenfeld, Z., and Pillar, C. (2013, January 10\u201313). In vitro synergy\/antagonism of the pleuromutilin BC-3781 with selected antibiotics against gram-positive and gram-negative bacteria. Proceedings of the 53th Interscience Conference on Antimicrobial Agents and Chemotherapy, Denver, CO, USA."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Gargvanshi, S., and Gutheil, W.G. (2022). Library screening for synergistic combinations of FDA-approved drugs and metabolites with vancomycin against VanA-type vancomycin-resistant Enterococcus faecium. Microbiol. Spectr., 10.","DOI":"10.1128\/spectrum.01412-22"},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Dong, C.L., Li, L.X., Cui, Z.H., Chen, S.W., Xiong, Y.Q., Lu, J.Q., Liao, X.P., Gao, Y., Sun, J., and Liu, Y.H. (2017). Synergistic effect of pleuromutilins with other antimicrobial agents against Staphylococcus aureus in vitro and in an experimental Galleria mellonella model. Front. Pharmacol., 8.","DOI":"10.3389\/fphar.2017.00553"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Xu, C., Zhang, Y., Ma, L., Zhang, G., Li, Y., Zeng, X., Li, Y., and Dong, N. (2024). Valnemulin restores colistin sensitivity against multidrug-resistant gram-negative pathogens. Commun. Biol., 7.","DOI":"10.1038\/s42003-024-06805-2"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Yu, Y., Fang, J.T., Zheng, M., Zhang, Q., Walsh, T.R., Liao, X.P., Sun, J., and Liu, Y.H. (2018). Combination therapy strategies against multiple-resistant Streptococcus Suis. Front. Pharmacol., 9.","DOI":"10.3389\/fphar.2018.00489"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2869","DOI":"10.1021\/acs.jmedchem.6b01805","article-title":"A new combination of a pleuromutilin derivative and doxycycline for treatment of multidrug-resistant Acinetobacter baumannii","volume":"60","author":"Siricilla","year":"2017","journal-title":"J. Med. Chem."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Chen, F., Wei, M.C., Luo, Y.D., Jin, Z., and Tang, Y.Z. (2020). Synergistic effect of a pleuromutilin derivative with tetracycline against Streptococcus suis in vitro and in the neutropenic thigh infection model. Molecules, 25.","DOI":"10.3390\/molecules25153522"},{"key":"ref_19","unstructured":"Clinical and Laboratory Standards Institute (2018). M07: Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically, Clinical and Laboratory Standards Institute. [11th ed.]."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"630","DOI":"10.1038\/s41429-020-0312-7","article-title":"In vitro synergistic effect of retapamulin with erythromycin and quinupristin against Enterococcus faecalis","volume":"73","author":"Park","year":"2020","journal-title":"J. Antibiot."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1093\/jac\/dkg301","article-title":"Synergy, antagonism, and what the chequerboard puts between them","volume":"52","author":"Odds","year":"2003","journal-title":"J. Antimicrob. Chemother."},{"key":"ref_22","unstructured":"Lorian, V. (2005). Antimicrobial combinations. Antibiotics in Laboratory Medicine, Lippincott Williams and Wilkins. [5th ed.]."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Terbtothakun, P., Nwabor, O.F., Siriyong, T., Voravuthikunchai, S.P., and Chusri, S. (2021). Synergistic antibacterial effects of meropenem in combination with aminoglycosides against carbapenem-resistant Escherichia coli harboring blaNDM-1 and blaNDM-5. Antibiotics, 10.","DOI":"10.3390\/antibiotics10081023"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"4489","DOI":"10.1128\/AAC.00358-13","article-title":"Antimicrobial activity of the pleuromutilin antibiotic BC-3781 against bacterial pathogens isolated in the SENTRY antimicrobial surveillance program in 2010","volume":"57","author":"Paukner","year":"2013","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1619","DOI":"10.1128\/AAC.05789-11","article-title":"Antimicrobial activity of the investigational pleuromutilin compound BC-3781 tested against Gram-positive organisms commonly associated with acute bacterial skin and skin structure infections","volume":"56","author":"Sader","year":"2012","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_26","unstructured":"(2024, October 11). Xenleta\u2014Summary of Product Characteristics. Available online: https:\/\/ec.europa.eu\/health\/documents\/community-register\/2022\/20220708156315\/anx_156315_en.pdf."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"418","DOI":"10.1007\/s40495-022-00297-6","article-title":"Lefamulin: A new hope in the field of community-acquired bacterial pneumonia","volume":"8","author":"Adhikary","year":"2022","journal-title":"Curr. Pharmacol. Rep."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Eyal, Z., Matzov, D., Krupkin, M., Paukner, S., Riedl, R., Rozenberg, H., Zimmerman, E., Bashan, A., and Yonath, A. (2016). A novel pleuromutilin antibacterial compound, its binding mode and selectivity mechanism. Sci. Rep., 6.","DOI":"10.1038\/srep39004"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"4433","DOI":"10.1128\/AAC.00594-16","article-title":"rRNA binding sites and the molecular mechanism of action of the tetracyclines","volume":"60","author":"Chukwudi","year":"2016","journal-title":"Antimicrob. Agents Chemother."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"460","DOI":"10.1038\/nrmicro2133","article-title":"Drug interactions and the evolution of antibiotic resistance","volume":"7","author":"Yeh","year":"2009","journal-title":"Nat. Rev. Microbiol."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1016\/j.mib.2020.05.012","article-title":"How antibiotics work together: Molecular mechanisms behind combination therapy","volume":"57","author":"Sullivan","year":"2020","journal-title":"Curr. Opin. Microbiol."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"a027037","DOI":"10.1101\/cshperspect.a027037","article-title":"Lincosamides, streptogramins, phenicols, and pleuromutilins: Mode of action and mechanisms of resistance","volume":"6","author":"Schwarz","year":"2016","journal-title":"Cold Spring Harb. Perspect. Med."},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Harms, J.M., Schlunzen, F., Fucini, P., Bartels, H., and Yonath, A. (2004). Alterations at the peptidyl transferase centre of the ribosome induced by the synergistic action of the streptogramins dalfopristin and quinupristin. BMC Biol., 2.","DOI":"10.1186\/1741-7007-2-4"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"946","DOI":"10.1261\/rna.078776.121","article-title":"Ribosomal RNA degradation induced by the bacterial RNA polymerase inhibitor rifampicin","volume":"27","author":"Hamouche","year":"2021","journal-title":"RNA"}],"container-title":["Microorganisms"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2607\/12\/12\/2515\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T16:48:17Z","timestamp":1760114897000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2607\/12\/12\/2515"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2024,12,6]]},"references-count":34,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2024,12]]}},"alternative-id":["microorganisms12122515"],"URL":"https:\/\/doi.org\/10.3390\/microorganisms12122515","relation":{},"ISSN":["2076-2607"],"issn-type":[{"value":"2076-2607","type":"electronic"}],"subject":[],"published":{"date-parts":[[2024,12,6]]}}}