Bactericidal and Anti-Biofilm Formation of Aqueous Plant Extracts against Pathogenic Bacteria

There is evidence of antibiotic resistance due to the formation of bacterial biofilm. The inhibition effect and biofilm formation is investigated by the use of aqueous extract from 13 plants against Shigella dysenteriae, pyogenes and Proteus mirabilis. Aqueous extracts were obtained by boiling and filtration. Antimicrobial activity was evaluated by extension of inhibition zone. Minimal inhibitory concentrations (MIC) of plant extracts were determined by broth dilution method. Assessment of biofilm formation was examined by tube assay method. Five plant extracts showed significant inhibition zones and subsequent MIC determination showed that garlic and ginger had 8, 8 and 16 mg/ml and 16, 8 and 8 mg/ml against S. dysenteriae, S. pyogenes and P. mirabilis respectively. Garlic and ginger also showed considerable reduction in biofilm formation of the three bacteria followed by cinnamon, clove and thyme that showed slight reduction in biofilm formation. Couple of the plants tested in this study had good bactericidal and anti-biofilm effects on S. dysenteriae, S. pyogenes and P. mirabilis. By the virtue of their inhibition properties they could therefore provide a potent alternative therapy for bacterial infection which overcomes the problem of resistance associated with antibiotic treatment.