Evaluation Of Synergistic Antimicrobial Activity Of Selected Medicinal Plant Extracts Against Multidrug-Resistant Bacteria From Hospital And Pharmaceutical Waste Soils In Himachal Pradesh

Abstract

The increasing prevalence of multidrug-resistant (MDR) bacteria, particularly in environments contaminated with antibiotics, poses a significant public health challenge. The present study aimed to isolate multidrug-resistant (MDR) bacterial strains from soil samples collected at pharmaceutical industry and hospital waste disposal sites in Himachal Pradesh, India, and to evaluate the synergistic antimicrobial potential of selected medicinal plant extracts against these isolates. Ten MDR bacterial strains, including Pseudomonas aeruginosa, Escherichia coli, Providencia rettgeri, Bacillus cereus, and Cellulosimicrobium cellulans, were identified using standard microbiological and molecular techniques. The antimicrobial activity of aqueous and ethanolic leaf extracts of Aegle marmelos, Terminalia chebula, Terminalia bellerica, Eucalyptus camaldulensis, and Jatropha curcas was assessed using the agar well diffusion assay. Synergistic combinations of extracts (S1–S4) showed enhanced antimicrobial effects compared to individual extracts, with S1 (A. marmelos + T. chebula, aqueous) and S3 (T. bellerica + T. chebula, ethanolic) demonstrating the highest activity. MIC and MBC values determined by the broth microdilution method confirmed the increased efficacy of these combinations. The results highlight the potential of synergistic plant extract formulations as alternative therapeutic agents against MDR bacterial infections.