CPP-PNA Conjugate-Mediated Inhibition of pdxA Gene Impairs Vitamin B6 Biosynthesis and Growth in Acinetobacter baumannii

TL;DR

A new CPP-PNA compound targeting the pdxA gene effectively inhibits vitamin B6 production and growth in Acinetobacter baumannii, a drug-resistant bacteria.

Contribution

The study introduces CPP-PNA conjugates as a novel antimicrobial strategy targeting vitamin B6 biosynthesis in multidrug-resistant A. baumannii.

Findings

CPP-PNA targeting pdxA suppressed A. baumannii growth at 1.56 μM.

The treatment reduced intracellular vitamin B6 by ~80%, indicating translational inhibition.

The CPP-PNA showed high specificity and no cytotoxicity in human cells.

Abstract

Acinetobacter baumannii represents a critical-priority organism due to its multidrug resistance. The emergence of carbapenem-resistant strains poses a major clinical challenge, underscoring the urgent need for novel antibacterial agents with alternative mechanisms. As peptide nucleic acids (PNAs) have recently gained attention as antisense therapeutics, we aimed to validate their potential as novel antimicrobial strategies against multidrug-resistant A. baumannii. We synthesized a cell-penetrating peptide (CPP)–PNA conjugate targeting pdxA, an essential gene involved in vitamin B6 biosynthesis. Among several candidate genes tested, the pdxA-targeting PNA exhibited the strongest inhibitory activity, achieving complete growth suppression of A. baumannii at 1.56 μM. Although quantitative real-time polymerase chain reaction did not reveal significant reductions in pdxA transcript levels, ELISA quantification revealed an approximately 80% reduction in intracellular vitamin B6, indicating translational inhibition rather than mRNA degradation. The pdxA-targeting CPP–PNA showed negligible activity against other Gram-negative or Gram-positive species, indicating high target specificity; no detectable cytotoxicity in human cells was observed even at relatively high concentrations. CPP–PNA conjugates targeting pdxA interfere with vitamin B6 biosynthesis, leading to growth inhibition of A. baumannii. These findings support PNA as a promising antisense antimicrobial platform that inhibits multidrug-resistant A. baumannii by blocking vitamin B6 biosynthesis.

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