Modulation of efflux pump gene expression in Enterococcus faecium by tungsten nanoparticles and multi-walled carbon nanotubes.

BACKGROUND

Enterococcus faecium (E. faecium) is an opportunistic pathogen frequently associated with urinary tract infections (UTIs). Its increasing multidrug resistance (MDR) is largely mediated by efflux pump systems that reduce intracellular antibiotic accumulation.

OBJECTIVE

This study aimed to investigate antimicrobial resistance patterns of clinical E. faecium isolates and to evaluate the antibacterial and efflux pump-modulating effects of tungsten nanoparticles (WNPs) and functionalized multi-walled carbon nanotubes (MWCNTs).

METHODS

Fifty-eight E. faecium isolates from UTI patients were subjected to antibiotic susceptibility testing and molecular detection of the efflux genes efrA, efrB, and emeA. WNPs and MWCNTs were synthesized, physicochemically characterized, and evaluated for antibacterial activity using minimum inhibitory concentration (MIC) assays. Quantitative real-time PCR was used to assess changes in efflux pump gene expression following nanoparticle exposure.

RESULTS

High resistance rates were observed for erythromycin (86.2%), tetracycline (81.0%), fluoroquinolones, and vancomycin (48.3%), with approximately 85% of isolates classified as MDR. Efflux pump genes were detected in 72-86% of isolates. WNPs and MWCNTs exhibited MIC values of 750 µg/mL and 375 µg/mL, respectively. Treatment with sub-inhibitory concentrations of these nanoparticles resulted in significant downregulation (1.8- to 2-fold) of efrA, efrB, and emeA expression, indicating suppression of efflux-mediated resistance mechanisms.

CONCLUSIONS

Tungsten nanoparticles and functionalized MWCNTs demonstrate notable antibacterial activity against MDR E. faecium and effectively modulate efflux pump gene expression. These findings support their potential use as adjunctive agents to enhance antimicrobial efficacy against resistant E. faecium infections, warranting further optimization and in vivo validation.