Abstract

In vitro time-kill kinetics antibacterial study of Acacia nilotica was assessed against Pseudomonas aeruginosa, Escherichia coli and Staphylococcus aureus determined by plate count technique and analyzed by percentage and log reduction. All test organisms were susceptible to the aqueous methanolic extract. The minimum inhibitory concentration ranged between 0.5 and 1 mg, while minimum bactericidal concentration ranged between ≥1 and ≥2 mg/ml. Average log reductions in viable cell counts for the extract ranged between 0.18log₁₀ and 0.35log₁₀ cfu/ml for P. aeruginosa, 0.27log₁₀ and 1.95log₁₀ cfu/ml for S. aureus and 0.27log₁₀ and 0.45log₁₀ cfu/ml for E. coli after 10 h interaction at 0.5x MIC and 1x MIC. Most of the extracts were rapidly bactericidal at 2x MIC achieving a complete elimination of most of the test organisms within 12 h exposure. A good correlation was found between the killing curves and the MIC of A. nilotica against the test organisms.

Key words: Time-kill kinetics, antibacteria, Acacia nilotica, percentage reduction.