What does this research mean for the field?

Colistin resistance in Acinetobacter baumannii isolates from South India is associated with specific mutations in the lpxA and pmrB genes, including four novel mutations, while the mcr-1 gene and mutations in pmrA, lpxC, and lpxD were not detected. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

To investigate the molecular mechanisms and specific gene mutations conferring resistance to the last-resort antibiotic colistin in clinical Acinetobacter baumannii isolates.

September 3, 2026AntibioticsOpen Access

Molecular Characterization of Colistin Resistance Acinetobacter baumannii Isolates and Identification of Mutations in pmrA and lpxA Genes from a Tertiary Care Hospital in South India

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Authors

MBMuthuLakshmi BackiaSubramanian MSMadhumala Shanmugasundaram SMShanthi MariappanSri Ramachandra Institute of Higher Education and Research

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Implication

Observational study reveals lpxA and pmrB gene mutations driving colistin resistance in Acinetobacter baumannii isolates, highlighting the decline of last-resort antimicrobial options.

Key Points

To investigate the molecular mechanisms and specific gene mutations conferring resistance to the last-resort antibiotic colistin in clinical Acinetobacter baumannii isolates.
Analyzed N=225 clinical isolates of Acinetobacter baumannii collected from a tertiary care hospital in South India.
Assessed antimicrobial susceptibility by disk diffusion according to CLSI M100 (Ed 35, 2025) guidelines and evaluated colistin susceptibility via microbroth dilution.
Investigated the presence of plasmid-mediated mcr genes alongside chromosomal alterations in pmrAB and lpxACD genes via conventional PCR and mutational analysis.
Identified colistin resistance in 4 of 225 clinical isolates (1.8%), with all resistant strains demonstrating an MIC ≥ 16 mcg/mL.
Detected mutations in lpxA and pmrB (specifically c.391T > C, c.495T > C, c.516A > G, c.732A > G, and c.966T > C), whereas no mutations were found in pmrA, lpxC, or lpxD.
Found no evidence of plasmid-borne mcr-1 gene transfer among the colistin-resistant isolates.

Cite This Study

BackiaSubramanian et al. (2026) studied this question.

synapsesocial.com/papers/6a993586636c6408cfa7dbb3 https://doi.org/10.3390/antibiotics15090846

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Implication

Observational study reveals lpxA and pmrB gene mutations driving colistin resistance in Acinetobacter baumannii isolates, highlighting the decline of last-resort antimicrobial options.

Molecular Characterization of Colistin Resistance Acinetobacter baumannii Isolates and Identification of Mutations in pmrA and lpxA Genes from a Tertiary Care Hospital in South India

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Implication

Key Points

Cite This Study

Molecular Characterization of Colistin Resistance Acinetobacter baumannii Isolates and Identification of Mutations in pmrA and lpxA Genes from a Tertiary Care Hospital in South India

Discussion

Member takes

Implication

Key Points

Cite This Study

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