Year: 2026
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Klebsiella pneumoniae poses a substantial health concern worldwide, with high mortality often associated with its elevated resistance levels. Combination antibiotic therapies have emerged as a viable strategy for addressing infections caused by these highly resistant pathogens, yet the evolutionary routes to resistance under such regimens remain poorly understood. Here, we investigated how resistance can emerge during exposure to combination therapy by conducting an in vitro evolutionary experiment with a clinical K. pneumoniae KPC-producing isolate (KP03, Brazil), which was initially susceptible to both amikacin and polymyxin B (AmkPol). While the combination therapy displayed an additive effect in vitro, subinhibitory exposure rapidly drove resistance. In three independent lineages, bacteria tolerated concentrations nearly 10-fold (polymyxin B) and 5-fold (amikacin) above EuCAST breakpoints, with MICs reaching 128–256 μg·mL –1 after 45 passages. These high resistance levels persisted for at least 10 days without selective pressure, although resistance lineages exhibited measurable fitness costs. Whole-genome sequencing revealed diverse mutations affecting lapB, phoP, rho, smbA, mlaA, and asmA, while transcriptomics analysis showed upregulation of the arn operon and the aphA alongside with downregulation of envelope- and efflux-associated genes. Cross-resistance was also observed against colistin and certain antimicrobial peptides, raising concern for treatment options beyond the AmkPol combination. Although combination therapy represents an important treatment strategy, our findings demonstrate that K. penumoniae can rapidly evolve stable, high-level resistance under combination therapy, highlighting the need for a deeper understanding of how such regimens influence resistance development and the continued need to develop novel antibiotics strategies.
Source: ACS Infectious Diseases
Language: English
Subfield: Molecular Medicine
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Funders: Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Killam Trusts, University of British Columbia, Fundação de Apoio à Pesquisa do Distrito Federal, Fundação de Apoio ao Desenvolvimento do Ensino, Ciência e Tecnologia do Estado de Mato Grosso do Sul, Universidade Católica de Brasília, Canadian Institutes of Health Research
Awards: G1738785605, G22113365, G3690646728
OpenAlex ID: W7128488029