Bioactive Phytol from Thymus vulgaris, a promising source of alternative medicine to combat blaKPC and blaOXA-48 genotypes of Klebsiella pneumoniae: A retrospective in vitro and in silico approach

Abstract

Carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a significant public health challenge due to its multidrug resistance and limited treatment options. This study investigates the antibacterial potential of Thymus vulgaris ethanolic extract and its bioactive compounds against multidrug-resistant K. pneumoniae strains harboring blaKPC and blaOXA-48 carbapenemase genes. The presence of these resistance genes was confirmed by multiplex PCR. The extract exhibited a dose-dependent inhibitory effect, with a maximum inhibition zone of 18 ± 1.5 mm at 100 μg. Chromatographic techniques, including thin-layer chromatography (TLC) and column chromatography, yielded six fractions, among which fraction F3 showed the strongest antibacterial activity. Gas chromatography-mass spectrometry (GC-MS) and ultra-performance liquid chromatography (UPLC) analyses identified phytol as the predominant bioactive constituent. Further evaluation of phytol revealed a minimum inhibitory concentration (MIC) of 125 μg/mL and a minimum bactericidal concentration (MBC) of 250 μg/mL against CRKP. Alamar Blue viability assays and bacterial culture confirmed phytol's bacteriostatic and bactericidal effects, independent of the ethanol solvent. These findings suggest that phytol inhibits bacterial growth, possibly through membrane-targeting mechanisms. Notably, this study is among the first to comprehensively assess phytol's efficacy against carbapenem-resistant K. pneumoniae strains carrying blaKPC and blaOXA-48 genes, integrating molecular characterization, chromatographic purification and antimicrobial activity. Overall, the results highlight phytol as a promising natural agent to combat multidrug-resistant bacterial infections and address the urgent global threat of antibiotic resistance.

Keywords: Antibacterials; Carbapenem-resistant enterobacteriacae; Klebsiella pneumoniae; Molecular docking; Phytol; Thymus vulgaris.