Evaluation of Antimicrobial Activity of Novel Chimeric M-PEX12 Peptide Against Acinetobacter baumannii.

BACKGROUND

Acinetobacter baumannii-induced nosocomial pneumonia and its associated biofilm infections pose significant clinical challenges due to high rates of antibiotic resistance. Traditional antibiotic treatments encounter numerous obstacles, making antimicrobial peptides (AMPs) a promising alternative for controlling such pathogens. The emergence of multidrug-resistant strains necessitates the exploration of innovative therapeutic strategies.

OBJECTIVES

We recently designed a novel hybrid peptide, M-PEX12, which exhibits antimicrobial activity and low toxicity in vitro. To confirm its therapeutic potential, we evaluated it in both in vitro and in vivo settings.

METHODS

M-PEX12 was evaluated using time-kill kinetics, thermal stability, reactive oxygen species (ROS) generation, biofilm inhibition assays, scanning electron microscopy (SEM), cytotoxicity tests, and virulence gene expression analysis. Its in vivo activity against A. baumannii was also assessed in an animal model.

RESULTS

The time-kill kinetics assay indicated that exposure to M-PEX12 at 1x minimum inhibitory concentration (MIC) (33/154) and 2x MIC resulted in over 95% reduction in bacterial populations within 30 minutes. Notably, the bacteria did not develop resistance to increased temperatures. M-PEX12 effectively disrupted biofilm formation at various concentrations. Field emission SEM revealed significant ultrastructural deformities in A. baumannii cell walls. Treatment with M-PEX12 increased production of intracellular ROS and decreased cell viability in a concentration-dependent manner. Cytotoxicity assays showed no significant effect on HEK293 cell viability. Additionally, expression levels of omp33, csuE, bfmR, and ompA were significantly reduced. The antimicrobial efficacy of M-PEX12 was confirmed in vivo.

CONCLUSIONS

M-PEX12 exhibited significant antimicrobial activity and low toxicity in a mouse model, suggesting its potential as a treatment for drug-resistant bacterial infections.