{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T18:59:33Z","timestamp":1785437973989,"version":"3.56.0"},"reference-count":46,"publisher":"American Veterinary Medical Association (AVMA)","license":[{"start":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T00:00:00Z","timestamp":1785369600000},"content-version":"unspecified","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["ajvr"],"published-print":{"date-parts":[[2026,7,30]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec id=\"sc_a1\">\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>\n                      Because of lefamulin\u2019s antimicrobial spectrum and intrapulmonary disposition, the objective of this study was to estimate MICs for macrolide- and rifampin-susceptible (MRS) and macrolide- and rifampin-resistant (MRR) isolates of\n                      <jats:italic>Rhodococcus equi<\/jats:italic>\n                      to lefamulin either alone or in combination with rifampin.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sc_a2\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      Gradient diffusion and broth microdilution were performed to determine MICs for lefamulin alone using MRS (n = 43) and MRR isolates (61) of\n                      <jats:italic>R equi<\/jats:italic>\n                      . Twenty MRR and 20 MRS isolates were tested for synergistic effects using a checkerboard assay and the fractional inhibitory concentration index as an outcome measure.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sc_a3\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>For both MRR and MRS isolates, MIC values were significantly higher using broth microdilution (median MIC, 32 \u00b5g\/mL; range, 8 to 64 \u00b5g\/mL) than gradient diffusion (median MIC, 12 \u00b5g\/mL; range, 5 to 28 \u00b5g\/mL) testing. The fractional inhibitory concentration values of MRR isolates (median, 0.562; range, 0.250 to 1.000) were significantly higher than those of MRS isolates (median, 0.280; range, 0.039 to 1.038). In addition, the proportion of isolates exhibiting synergistic interaction was significantly greater among MRS isolates (16 of 20 [80%]) than among MRR isolates (6 of 20 [30%]).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sc_a4\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>\n                      Overall, the MIC values for lefamulin against\n                      <jats:italic>R equi<\/jats:italic>\n                      were high relative to concentrations considered therapeutic in humans. When combined with rifampin, lefamulin exhibited synergistic effects for MRS but not MRR isolates.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sc_a5\">\n                    <jats:title>Clinical Relevance<\/jats:title>\n                    <jats:p>Need exists for alternative antimicrobials to treat rhodococcal foal pneumonia. Results indicate that studies in foals of the pharmacokinetics and pulmonary disposition of lefamulin in combination with rifampin are warranted.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.2460\/ajvr.26.05.0213","type":"journal-article","created":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T18:27:16Z","timestamp":1785436036000},"page":"1-9","source":"Crossref","is-referenced-by-count":0,"title":["Combining lefamulin with rifampin provides in vitro synergistic antimicrobial effects against Rhodococcus equi isolates susceptible to macrolides and rifampin"],"prefix":"10.2460","author":[{"given":"Sally F. O.","family":"Alpini","sequence":"first","affiliation":[{"name":"Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Marlane G.","family":"Seeger","sequence":"additional","affiliation":[{"name":"Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX"},{"name":"Department of Veterinary Preventive Medicine, Faculty of Veterinary Medicine, Federal University of Santa Maria, Santa Maria, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Bibiana P.","family":"da Silveira","sequence":"additional","affiliation":[{"name":"Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cierra A.","family":"Cadena","sequence":"additional","affiliation":[{"name":"Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Elaine","family":"Pham","sequence":"additional","affiliation":[{"name":"Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laura","family":"Huber","sequence":"additional","affiliation":[{"name":"Department of Veterinary Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Angela I.","family":"Bordin","sequence":"additional","affiliation":[{"name":"Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jing","family":"Wu","sequence":"additional","affiliation":[{"name":"Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sara D.","family":"Lawhon","sequence":"additional","affiliation":[{"name":"Department of Veterinary Pathobiology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0384-2903","authenticated-orcid":true,"given":"Noah D.","family":"Cohen","sequence":"additional","affiliation":[{"name":"Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1272","reference":[{"issue":"6","key":"B1","series-title":"J Vet Intern Med","first-page":"1221","article-title":"Rhodococcus equi: clinical manifestations, virulence, and immunity","volume":"25","author":"Gigu\u00e8re S","year":"2011","unstructured":"Gigu\u00e8re S, Cohen ND, Keith Chaffin M, et al. 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