{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T18:04:19Z","timestamp":1780682659670,"version":"3.54.1"},"reference-count":19,"publisher":"Public Library of Science (PLoS)","issue":"6","license":[{"start":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T00:00:00Z","timestamp":1780617600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100003593","name":"Conselho Nacional de Desenvolvimento Cient\u00edfico e Tecnol\u00f3gico","doi-asserted-by":"publisher","award":["408778\/2022-9, 307946\/2022-3, 444735\/2023-2, and 405785\/2024-0"],"award-info":[{"award-number":["408778\/2022-9, 307946\/2022-3, 444735\/2023-2, and 405785\/2024-0"]}],"id":[{"id":"10.13039\/501100003593","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100005672","name":"Funda\u00e7\u00e3o de Apoio ao Desenvolvimento do Ensino, Ci\u00eancia e Tecnologia do Estado de Mato Grosso do Sul","doi-asserted-by":"publisher","award":["325\/2022, 76\/2023 and 113\/2023"],"award-info":[{"award-number":["325\/2022, 76\/2023 and 113\/2023"]}],"id":[{"id":"10.13039\/501100005672","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002322","name":"Coordena\u00e7\u00e3o de Aperfei\u00e7oamento de Pessoal de N\u00edvel Superior","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100002322","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100020983","name":"Universidade Federal da Grande Dourados","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100020983","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"\n Background<\/jats:title>\n \n Multidrug-resistant\n Klebsiella pneumoniae<\/jats:italic>\n , including carbapenem- and polymyxin-resistant strains, poses a major public health threat by severely limiting therapeutic options. Although ceftibuten (CTB) and polymyxin B (PMB) show evidence of synergistic activity, their mechanisms of action remain unclear. In this context, this study evaluated the combined effect of CTB and PMB on the expression of genes involved in cell wall synthesis and antimicrobial resistance in\n K. pneumoniae<\/jats:italic>\n .\n <\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n Protein sequences of selected resistance- and cell wall-related genes were retrieved from UniProt and analyzed\n in silico<\/jats:italic>\n for conserved domains, motifs, localization (PSORTb), and pathways (KEGG). The effects of CTB\/PMB, alone and in combination, were evaluated on the expression of genes involved in cell wall synthesis regulation (\n ftsL, dacA,<\/jats:italic>\n and\n dacC<\/jats:italic>\n ) and antimicrobial resistance mechanisms (\n pagP, pagL, ampC)<\/jats:italic>\n . The 16s gene was used as endogenous control. Bacterial cultures (1.5\u2009\u00d7\u200910\n 6<\/jats:sup>\n CFU\/mL) were incubated with CTB\/PMB, PMB and CTB at 0.5\u00d7 and 1\u2009\u00d7\u2009minimum inhibitory concentrations (MIC) for 2 and 4 h, followed by mRNA extraction and gene expression analysis through qRT-PCR.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n In silico<\/jats:italic>\n analyses revealed that\n pagP<\/jats:italic>\n and\n pagL<\/jats:italic>\n contain conserved domains associated with lipid A modification, while\n ampC<\/jats:italic>\n and\n ftsL<\/jats:italic>\n showed class C \u03b2-lactamase domains.\n DacA<\/jats:italic>\n and\n dacC<\/jats:italic>\n were linked to the PRK13482 domain of the cl44310 superfamily. Predicted localizations placed\n pagP\/pagL<\/jats:italic>\n in the outer membrane,\n ampC<\/jats:italic>\n in the periplasm, and\n ftsL\/dacA\/dacC<\/jats:italic>\n in the cytoplasmic membrane. KEGG annotation indicated that\n ftsI<\/jats:italic>\n ,\n dacC<\/jats:italic>\n ,\n ampC<\/jats:italic>\n , and\n rtxB<\/jats:italic>\n participate in essential pathways, including peptidoglycan biosynthesis and \u03b2-lactam resistance, highlighting their physiological and clinical relevance in\n K. pneumoniae<\/jats:italic>\n . After 2 h of exposure, no significant changes were observed in the expression of the selected genes. However, after 4 h,\n dacA, ftsL,<\/jats:italic>\n and\n pagP<\/jats:italic>\n expression levels significantly increased in all groups treated with CTB\/PMB. Additionally,\n dacC<\/jats:italic>\n and\n pagL<\/jats:italic>\n expression were upregulated in the group treated with the combination at 1\u2009\u00d7\u2009MIC.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusions<\/jats:title>\n \n Thus, combined CTB\/PMB exposure was associated with modulation of gene expression involved in cell wall synthesis and antimicrobial resistance, suggesting transcriptional adaptive responses under antimicrobial pressure. These findings provide preliminary molecular insights into the response of multidrug-resistant\n K. pneumoniae<\/jats:italic>\n to CTB\/PMB exposure.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.1371\/journal.pone.0349583","type":"journal-article","created":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T17:35:53Z","timestamp":1780680953000},"page":"e0349583","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["Ceftibuten-polymyxin B combination alters resistance and cell wall gene expression in multidrug-resistant Klebsiella pneumoniae"],"prefix":"10.1371","volume":"21","author":[{"given":"Mariana Carvalho","family":"Sturaro","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0435-1871","authenticated-orcid":true,"given":"Ruana Carolina Cabral 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