{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,10]],"date-time":"2026-10-10T13:22:52Z","timestamp":1791638572239,"version":"4.3.4"},"reference-count":35,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,6,9]],"date-time":"2026-06-09T00:00:00Z","timestamp":1780963200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100008108","name":"Taipei Tzu Chi Hospital","doi-asserted-by":"crossref","award":["TCRD-TPE-NCU-115-03"],"award-info":[{"award-number":["TCRD-TPE-NCU-115-03"]}],"id":[{"id":"10.13039\/501100008108","id-type":"DOI","asserted-by":"crossref"}]},{"award":["TCRD-TPE-NCU-115-03"],"award-info":[{"award-number":["TCRD-TPE-NCU-115-03"]}],"id":[{"id":"https:\/\/ror.org\/00q017g63","id-type":"ROR","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100005925","name":"Buddhist Tzu Chi Medical Foundation","doi-asserted-by":"crossref","award":["TCRD-TPE-114-04(2\/3)"],"award-info":[{"award-number":["TCRD-TPE-114-04(2\/3)"]}],"id":[{"id":"10.13039\/501100005925","id-type":"DOI","asserted-by":"crossref"}]},{"award":["TCRD-TPE-114-04(2\/3)"],"award-info":[{"award-number":["TCRD-TPE-114-04(2\/3)"]}],"id":[{"id":"https:\/\/ror.org\/04rbvc675","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Antibiotics"],"abstract":"<jats:p>Background\/Objectives:\u00a0Staphylococcus haemolyticus is a common skin commensal that has emerged as a multidrug-resistant nosocomial pathogen, with sequence type 42 frequently implicated in clinical settings. The genetic basis of fusidic acid (FA) resistance mediated by mutations in elongation factor-G (fusA\/EF-G) has not been systematically characterized in S. haemolyticus. Methods: Five representative FA-susceptible S. haemolyticus isolates were selected. In vitro FA resistance was induced by incubating each isolate on Mueller\u2013Hinton agar containing 4 \u00b5g\/mL FA at 37 \u00b0C for 48 h. Resistant colonies were recovered and fusA was sequenced by Sanger sequencing to identify mutations. Growth doubling times of EF-G mutant isolates were measured and compared with those of the parental susceptible strains. Potential fitness-compensatory changes in fusA were assessed by serial passage of selected mutants for ten successive passages and re-sequencing of fusA. Results: A total of 28 FA-resistant colonies were recovered. Sequencing identified mutations at seven nucleotide loci corresponding to ten distinct amino acid substitutions in EF-G: Q115L, L430S, E433G, G452C, H457Y, H457N, H457L, H457Q, R464L, and A655G. The mean doubling time of EF-G mutant isolates was significantly longer than that of the wild-type parental strains (mutants: 55.75 \u00b1 7.78 min, n = 28; wild type: 40.78 \u00b1 4.13 min, n = 5; Welch\u2019s two-sample t test: t = \u22126.34, df \u2248 10.0, two-tailed p &lt; 0.0001). Following ten serial passages, we did not detect compensatory mutations in fusA that restored the ancestral growth rate. Conclusions: FA resistance in S. haemolyticus can be rapidly induced in vitro through mutations in EF-G\/fusA. Compared with previously reported EF-G mutations in other staphylococci, we identified two novel substitution sites (L430S, E433G) and previously unreported substitutions at established resistance positions (H457N, H457L, A655G). Mutations in EF-G (encoded by fusA) were associated with a measurable in vitro fitness cost; following ten serial passages, compensatory mutation was not detected in fusA. These findings support systematic surveillance of EF-G\/fusA mutations in clinical S. haemolyticus isolates. Further studies should address their prevalence, stability, transmissibility, and clinical impact, particularly where FA use is increasing and patient populations are vulnerable.<\/jats:p>","DOI":"10.3390\/antibiotics15060589","type":"journal-article","created":{"date-parts":[[2026,6,10]],"date-time":"2026-06-10T06:33:44Z","timestamp":1781073224000},"page":"589","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Elongation Factor-G (fusA) Mutations That Confer Fusidic Acid Resistance in Staphylococcus haemolyticus"],"prefix":"10.3390","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6668-0182","authenticated-orcid":false,"given":"Cheng-Mao","family":"Ho","sequence":"first","affiliation":[{"name":"Division of Clinical Pathology, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung 427213, Taiwan"},{"name":"Division of Laboratory Medicine, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung 427213, Taiwan"},{"name":"Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien 970374, Taiwan"},{"name":"Department of Pathology, School of Medicine, Tzu Chi University, Hualien 970374, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5858-6214","authenticated-orcid":false,"given":"Lee-Chung","family":"Lin","sequence":"additional","affiliation":[{"name":"Department of Laboratory Medicine, Linkou Chang Gung Memorial Hospital, Taoyuan 333423, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0001-2821-4882","authenticated-orcid":false,"given":"Yu-Hsiang","family":"Ou","sequence":"additional","affiliation":[{"name":"Department of Laboratory Medicine, Linkou Chang Gung Memorial Hospital, Taoyuan 333423, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kai-Hsiang","family":"Lin","sequence":"additional","affiliation":[{"name":"Division of Laboratory Medicine, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung 427213, Taiwan"},{"name":"Department of Laboratory Medicine and Biotechnology, College of Medicine, Tzu Chi University, Hualien 970374, Taiwan"},{"name":"Department of Life Sciences, National Chung Hsing University, Taichung 40227, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1692-1707","authenticated-orcid":false,"given":"Jang-Jih","family":"Lu","sequence":"additional","affiliation":[{"name":"Division of Clinical Pathology, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei 231405, Taiwan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"a025437","DOI":"10.1101\/cshperspect.a025437","article-title":"Fusidic Acid: A Bacterial Elongation Factor Inhibitor for the Oral Treatment of Acute and Chronic Staphylococcal Infections","volume":"6","author":"Fernandes","year":"2016","journal-title":"Cold Spring Harb. 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