# Camellia sinensis-synthesized silver nanoparticles and meropenem combination against extensively drug-resistant Klebsiella pneumoniae

## TL;DR

This study shows that combining silver nanoparticles made from green tea with the antibiotic meropenem can effectively fight drug-resistant Klebsiella pneumoniae bacteria.

## Contribution

The novel contribution is the development and testing of Camellia sinensis-synthesized silver nanoparticles in combination with meropenem against XDR Klebsiella pneumoniae.

## Key findings

- Most Klebsiella pneumoniae isolates were extensively drug-resistant (XDR), with 92.5% identified as XDR.
- The combination of AgNPs and meropenem showed synergistic effects, with 65.5% showing complete synergy against XDR strains.
- AgNPs alone had antimicrobial activity with inhibition zones ranging from 10 mm to 25 mm.

## Abstract

New strategies against antimicrobial resistance are urgently needed to address the challenges and health consequences posed by extensively drug-resistant (XDR) clinical isolates. This study explored how effective the green-synthesized silver nanoparticles alone or in combination with meropenem are in combating XDR Klebsiella pneumoniae. Klebsiella pneumoniae (K. pneumoniae) isolates were collected from several clinical labs and identified. After carrying out antimicrobial susceptibility testing, XDR isolates were selected for genotypic analysis using ERIC-PCR, and antibiotic resistance genes were identified. Silver nanoparticles (AgNPs) were synthesized using a Camellia sinensis (green tea) extract and characterized using UV-Vis spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Particle size analysis was conducted to determine the physicochemical properties of the synthesized AgNPs. The AgNPs antibacterial effect alone or in combination with meropenem was carried out using the agar-well diffusion method, and the minimum inhibitory concentration (MIC), multiple antibiotic resistance (MAR) index and fractional inhibitory concentration index (FICI) were determined. Of the collected isolates, 67 were identified as K. pneumoniae, and 92.5% were considered XDR. Results showed that 10 (14.9%) and 57 (85.1%) isolates exhibited MAR index from 0.58 to 0.74, and 0.79-1.00, respectively. Upon genotypic analysis, 29 isolates were selected for further studies based on their unique or significant clustering patterns. The synthesized AgNPs exhibited strong antimicrobial activity against XDR K. pneumoniae strains, with inhibition zones ranging from 10 mm to 25 mm. The MIC of AgNPs ranged from 336.17 to 672.35 µg/mL. The fractional inhibitory concentration index (FICI) proved enhanced antimicrobial activity with partial (34.5%) and complete synergistic (65.5%) effects in the tested 29 nonclonal clinical isolates when AgNPs were combined with meropenem. In conclusion, a combination of AgNPs with meropenem is a useful alternative approach in combating XDR K. pneumoniae. Further studies are recommended for the use of this approach in clinical settings based on its benefits to enhance treatment outcomes.

The online version contains supplementary material available at 10.1038/s41598-026-38375-0.