Interactions Between Leaf Extracts of <i>Ageratum conyzoides</i> and Antibiotics Against Clinical Strains of <i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i>

Abstract

The antibacterial effects of Ageratum conyzoides aqueous and alcoholic leaf extracts against Staphylococcus aureus and Pseudomonas aeruginosa were determined using spread plate, disc diffusion and tube dilution procedures. The antibiogram profiles of both S. aureus and P. aeruginosa were determined using disc diffusion method. The synergistic activity of the mixture of 200 mg/ml leaf extract concentrate and the respective antibiotics; Ciprofloxacin, Norfloxacin and Septrin against P. aeruginosa and S.aureus was evaluated using both spread plate and disc diffusion methods. The aqueous leaf extract elicited an inhibitory zone diameter of inhibition ranging from 6mm to 10mm for S. aureus; 7mm to 12mm for P. aeruginosa. P. aeruginosa and S.aureus exposed to the methanolic leaf extract displayed zones which ranged from 9mm to 15mm and 10mm to 16mmrespectively. S. aureus was resistant to all antibiotics except for Norfloxacin, Septrin and Ciprofloxacin, while P. aeruginosa was susceptible to ciprofloxacin alone. The synergism between the leaf extracts and the selected antibiotics showed greater inhibitory zones against the test isolates as against exposure to only the selected antibiotics. The results indicated the potential health benefits of the use of antibiotics in combination with decoctions from known medicinal plants.

Keywords: Disc diffusion method, antimicrobial activity, A. conyzoides, synergistic action, methanolic extract