Evaluation of antimicrobial and synergistic effects of some medicinal plant extracts on antimicrobial resistant organisms

Abstract

Background: To evaluate antimicrobial activity of ten plant extracts on antimicrobial resistant organisms and investigate interactions of these extracts with antimicrobials against resistant organisms. Methods: The antimicrobial potential of ethanolic leaf extract of Aberia caffra Hook. f. & Harv., Azadirachta indica L., Dodonaea viscosa L., Ficus nitida L., Lanatana camara L., Myrtus communis L., Olea europaea L., Ruta graveolens, Schinus terebinthifolius Raddi and Vitex agnus-castus L. was investigated against eleven drug resistant organisms by agar well diffusion method. The interaction of these extracts with antimicrobials was assessed. Results: Ethanolic extracts of Dodonaea viscosa leaves had antibacterial activity against ESBL-producing Escherichia coli (E. coli) quinolone resistant Salmonella typhi (S. typhi) and ESBL and carbapenemase-producing Klebsiella pneumonia (K. pneumonia). Schinus terebinthifolius Raddi leaves showed antibacterial activity against ESBL and carbapenemase-producing K. pneumoniae and fluconazole resistant C. albicans. Myrtus communis leave extracts demonstrated activity against ESBLproducing E. coli and fluconazole resistant A. fumigatus. Ruta graveolens L. revealed activity against quinolone resistant S. typhi and fluconazole resistant A. fumigatus. Vitex agnus-castus, Aberia caffra Hook. f. & Harv. and Azadirachta indica L. leaf extracts had activity against ESBL-producing E. coli. Olea europaea L. had activity against quinolone resistant A. baumannii. Ruta graveolens L. and Myrtus communis L. were the only extracts showing synergistic effect in association with voriconazole against fluconazole resistant A. fumigatus. Conclusion: Tested plant leaf extracts had great potential as antimicrobial agents against at least one drug resistant microorganism. Isolation of active components and further studies are needed to evaluate the efficacy and toxicity of these products.