Antimicrobial activity of Palestinian medicinal plants against acne-inducing bacteria

The antimicrobial activities of 56 Palestinian medicinal plants against etiologic agents of acne vulgaris, mainly Propionibacterium acnes and Staphylococcus aureus was studied using disc diffusion and broth dilution methods. The results from the disc diffusion method demonstrated that these plants differ significantly in their activity against the studied microorganisms. The most active plants against all bacterial strains were Rhus coriaria, Ricinus communis, and Sarcopoterium spinosum. Test microorganisms differed significantly in relation to their susceptibility to different plant extracts used. Generally, anaerobic bacteria were more susceptible to plant extracts than aerobic bacteria. Those plants which could inhibit the growth of P. acnes, R. coriaria, R. communis, and S. spinosum had strong inhibitory effects. 43 plants could inhibit the growth of all aerobic bacteria. Based on a broth dilution method, the R. coriaria extract had the greatest antimicrobial effect against P. acnes (MIC 6 mg/ml, MBC 6 mg/ml), S. aureus (MIC 4 mg/ml, MBC 6 mg/ml), E. coli (MIC 6 mg/ml, MBC 8 mg/ml) and P. aeruginosa (4 and 6 mg/ml). Taken together, our data indicate that R. coriaria, R. communis had a strong inhibitory effect on P. acnes and most other test bacteria. Therefore, the two plants would be an interesting topic for further study and possibly for an alternative treatment for acne.   Key words: Acne, Propionibacterium acnes, Staphylococcus aureus, Echerichia coli,Klebsiella pneumonia, Proteus vulgaris, antimicrobial activity.