In vitro antimicrobial activities of 26 Yunnan plant extracts against multi-drug resistant pathogens

In vitro activities of 80% ethanol extracts from 26 plants native to South-Eastern Yunnan, China, were evaluated against clinical multi-drug resistant (MDR) pathogens. The extracts were initially screened by the agar hole diffusion test. Then the minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) or minimum fungicidal concentration (MFCs) were determined through serial dilution with a standard broth micro-dilution method. Of the 26 extracts, 9 showed different potencies against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Candida albicans. The most active plants against both S. aureus and methicillin-resistant S. aureus (MRSA) were Rhodoleia parvipetala Tong, Diplopanax stachyanthus Hand.-Mazz and Sarcosperma kachinense Exell var. simondii Lam. et Royen, and their MIC/MBCs were 512, 512, 256-512 mg/L, respectively. Sladenia celastrifolia Kurz extract showed strong activity against P. aeruginosa and C. albicans, and their MICs were 512-2048 and 2048 mg/L, together with no activities of MBC or MFC up to the concentrations of 2048 mg/L. All these plants showed weak inhibition against E. coli.