Antibiotic resistance, a growing concern for various reasons, underscores the urgency of discovering new antibiotics. However, the emergence of resistance mechanisms remains a formidable challenge. One such mechanism is the efflux pumps, which actively extrude antibiotics from bacterial cells, reducing their intracellular concentrations. Inhibiting these pumps can restore antibiotic efficacy. Natural sources are actively explored for potential inhibitors. This study aimed to assess the inhibitory potential of a methanol extract from the macrofungus Phellinus hartigii against multidrug-resistant (MDR) E. coli strains known to harbour active efflux pumps. These strains exhibited resistance to Amoxicillin-Clavulanate (AMC) with a MIC >32/2 (R). Inhibition was initially determined using the Ethidium Bromide (EtBr) test. Subsequently, combination studies involving the strain, antibiotic disks, and the extract revealed that the extract effectively arrested microorganism growth. Gas Chromatography-Mass Spectrometry (GC/MS) analysis of the extract identified major components, notably 2-methylhexacosane (59.10%) and Nonadecyl heptafluorobutyrate, which accounted for over 9% of the total area. Fourier transform infrared spectroscopy (FTIR) analysis of the strain treated with a combination of the extract and antibiotic provided insights into the inhibitory mechanism. Significant differences were observed in FTIR peaks, particularly in the region between <900 cm ^-1 and 3000 cm ^-1 . These findings warrant further investigation to elucidate the inhibitory effects comprehensively.
Acknowledgement: This study was supported by the Kastamonu University Scientific Research Project
(KÜBAP-01-2021-47).