Abstract

Concurrent administration of orthodox and herbal antibacterial agents could help overcome the tendency with which the former is inactivated by bacterially-produced endogenous enzymes. This study was designed to evaluate the antimicrobial interaction between the ethanol extract ofCardiospermum grandiflorum leaf (CGL) which is used in a remote village in Nsukka, Nigeria as a bathing sponge for treatment of skin infections  and amoxicillin (AMX), an extended-spectrum but penicillinase-susceptible penicillin. The antimicrobial interaction between these two agents was evaluated by modification of the checkerboard technique usingStaphylococcus aureus (a penicillinase-producing Gram-positive bacterium)and Bacillus subtilis (a non penicillinase-producing Gram-positive bacterium) as the test organisms. The MIC of the ethanolic extract against S. aureus and B. subtilis was respectively, 25.0 ± 0.1 and 50.0 ± 0.5 mg/ml while the MICs of amoxicillin were  0.05 ± 0.01  and  0.025 ± 0.002 mg/ml against  B.  subtilis and S. aureus, respectively. The effect of combination of the ethanol extract of C. grandiflorum leaf with amoxicillin was dependent on both the ratio of combination and the test organism employed for the evaluation. Overall, the combined antimicrobial effect was predominantly synergistic against S. aureus.

Key words: Cardiospermum grandiflorum leaf, antibacterial interaction, checkerboard technique, Bacillus subtilis, Staphylococcus aureus, amoxicillin.

Abbreviation

CGL, Cardiospermum grandiflorum  leaf ethanolic extract; AMX, Amoxicillin;FIC_AMX, fractional inhibitory concentration of amoxicillin; FIC_CGL, fractional inhibitory concentration of C. grandiflorum leaf ethanolic extract; Syn, synergism; Add, additivity; Ind,indiffernce; Ant, antagonism.