Comparative studies on the antibacterial activities of leaf extracts of Azadirachta indica and Psidium guajava and antibiotics on methicillin and vancomycin resistant Staphylococcus aureus

Objective: This study investigated the antibacterial activity of the acetone, methanol, and ethanol leaf extracts of Azadirachta indica and Psidium guajava against methicillin resistant Staphylococcus aureus ( MRSA) and vancomycin resistant Staphylococcus aureus (VRSA) strains as well as the antimicrobial activity of some conventional antibiotics on these multidrug resistant organisms. Methods: MRSA and VRSA strains were obtained from the culture collection unit of a tertiary hospital in Ebonyi State, Nigeria. The test organisms and the plant extracts were processed using standard microbiology techniques. Kirby-Bauer disk diffusion technique was used to determine the antimicrobial susceptibility profile of the MRSA and VRSA strains to some conventionally used antibiotics; and the antibacterial activity of the plant extracts was evaluated using agar well diffusion technique with three solvents: ethanol, methanol and acetone. Results: It was revealed in this study that the extracts of A. indica and P. guajava demonstrated some level of antimicrobial activity against the test organism at concentrations of 100 mg/ml and 50 mg/ml. Compared to the conventional antibiotics used, the antibiotics showed better antimicrobial activity against the test organisms than the plant extracts which was least active against the MRSA and VRSA strains. Conclusions: Though the A. indica and P. guajava extracts showed some appreciable antimicrobial activity against the MRSA and VRSA strains, the conventional antibiotics produced better antimicrobial action against these multidrug resistant bacteria. The search for novel compounds with putative antimicrobial activity should be stepped up since plants holds the potential for discovering novel drugs.