{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,27]],"date-time":"2026-04-27T18:32:02Z","timestamp":1777314722230,"version":"3.51.4"},"reference-count":48,"publisher":"Public Library of Science (PLoS)","issue":"4","license":[{"start":{"date-parts":[[2026,4,27]],"date-time":"2026-04-27T00:00:00Z","timestamp":1777248000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010269","name":"Wellcome Trust","doi-asserted-by":"publisher","award":["220690\/Z\/20\/Z"],"award-info":[{"award-number":["220690\/Z\/20\/Z"]}],"id":[{"id":"10.13039\/100010269","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosntds.org"],"crossmark-restriction":false},"short-container-title":["PLoS Negl Trop Dis"],"abstract":"\n Background<\/jats:title>\n \n Murine typhus, caused by\n Rickettsia typhi<\/jats:italic>\n , is a treatable febrile illness in Laos, where azithromycin treatment failure has been reported. Antibiotic susceptibility testing for\n Rickettsia<\/jats:italic>\n spp. is challenging due to absence of resistant strains. We aimed to induce an azithromycin-resistant in\n R. typhi<\/jats:italic>\n and investigate its genetic basis.\n <\/jats:p>\n <\/jats:sec>\n \n Methodology<\/jats:title>\n \n R. typhi<\/jats:italic>\n Wilmington was cultured in azithromycin-containing media (\n R. typhi<\/jats:italic>\n AZM<\/jats:sup>\n ), starting at a concentration of 0.0019 mg\/L and gradually increased to 0.0625 mg\/L. Resistant populations were selected up to 0.125 mg\/L. MICs were determined using plaque assay and qPCR, and DNA sequencing was performed for\n rplD<\/jats:italic>\n (L4\n ), rplV<\/jats:italic>\n (L22), and 23S rRNA domain V. Protein modeling of azithromycin-binding sites was conducted, and strain stability was assessed over 24 passages without azithromycin (\n R. typhi<\/jats:italic>\n AZM (-)<\/jats:sup>\n ).\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n MICs for wild type (\n R. typhi<\/jats:italic>\n WT<\/jats:sup>\n ) and\n R. typhi<\/jats:italic>\n AZM<\/jats:sup>\n were 2 mg\/L versus >16 mg\/L (plaque assay) and 0.25 mg\/L versus 8 mg\/L (qPCR). A 15-nucleotides insertion (5\u2019-AAAGGAAGAGCAACT-3\u2019) was found in the\n rplV<\/jats:italic>\n of\n R. typhi<\/jats:italic>\n AZM<\/jats:sup>\n , but not other isolates. Protein modeling suggested the insertion extends the L22 loop, potentially affecting azithromycin binding site within the ribosomal exit tunnel.\n R. typhi<\/jats:italic>\n AZM<\/jats:sup>\n reverted to wild type MIC and genotype by 24 passages without azithromycin.\n R. typhi<\/jats:italic>\n AZM<\/jats:sup>\n exhibited an 8 -fold higher MIC than\n R. typhi<\/jats:italic>\n WT<\/jats:sup>\n .\n <\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n \n Repetitive insertion in\n rplV<\/jats:italic>\n was associated with azithromycin resistance and may interfere with drug binding\n . R. typhi<\/jats:italic>\n AZM<\/jats:sup>\n was unstable without selective pressure. This approach may help generate resistant strains for assay validation. The role of\n rplV<\/jats:italic>\n mutations in azithromycin susceptibility warrants further investigation.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.1371\/journal.pntd.0014249","type":"journal-article","created":{"date-parts":[[2026,4,27]],"date-time":"2026-04-27T17:31:42Z","timestamp":1777311102000},"page":"e0014249","update-policy":"https:\/\/doi.org\/10.1371\/journal.pntd.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["A repetitive nucleotide insertion in the rplV gene is associated with in vitro resistance to azithromycin in Rickettsia typhi"],"prefix":"10.1371","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-1468-5138","authenticated-orcid":true,"given":"Weerawat","family":"Phuklia","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kiattawee","family":"Chowongkomon","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kaisone","family":"Padith","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Koukeo","family":"Phommasone","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mayfong","family":"Mayxay","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Allen L.","family":"Richards","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Elizabeth M.","family":"Batty","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Matthew T.","family":"Robinson","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Paul N.","family":"Newton","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nicholas J.","family":"White","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Nicholas P. 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