Antibacterial Activities of some Ghanaian Medicinal Plants against Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Sensitive Staphylococcus aureus (MSSA)

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JUNE, 2016
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Plants are noted to have nutritional properties as well as a reservoir for potential drug production and have been part of phytomedicine for many years. Several reports on the antimicrobial activity of different herbs have been documented. Synthetic antibiotics have been the main therapy for resistant bacterial infections; however, the misuse and overuse of antibiotics have become the main factor for the emergence of drug resistant strains of several groups of microorganisms, hence the need to investigate the antimicrobial properties of medicinal plants. The antibacterial activities of the selected plant leaf extracts of various concentrations (100, 150, 200 mg/ml) were tested against clinical isolates of Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Sensitive Staphylococcus aureus (MSSA) as well as seven standard strains of bacteria (K. pneumoniae ATCC 33495, Proteus mirabilis ATCC 49565, S. saprophyticus ATCC 15305, Salmonella typhi ATCC 19430, S. aureus ATCC 25923, E. coli ATTC 25922 and P. aeruginosa ATCC 27853) using modified agar diffusion and minimum inhibitory concentration (MIC) methods. Phytochemical analyses identified compounds such as alkaloids, flavonoids, saponins, tannins, phenols, cardiac glycosides, and terpenoids. Alchornea cordifolia gave the highest inhibitory effect (P < 0.0011) followed by Psidium guajava (P < 0.0142) against MRSA whilst the rest of the plants showed no inhibitory effect. Psidium guajava, Alchornea cordifolia, Phyllanthus fraternus, Cnestis ferruginea and Hoslundia opposita had significant effect on the MSSA and the standard bacterial strains (P < 0.05). Both leaf extracts of Alchornea cordifolia and Psidium guajava were highly effective against the MRSA strains with MIC value of 0.195 mg/ml. Generally, the ethanol extracts of the plants had higher antibacterial activity than aqueous extracts. All the standard bacteria strains were susceptible to the selected medicinal plants with the exception of K. pneumoniae which was not susceptible even to Alchornea cordifolia and Psidium guajava. Amongst the seven different plants, Alchornea cordifolia and Psidium guajava inhibited the growth of resistant isolates of MRSA, and therefore, can be good sources of antimicrobial production which could significantly inhibit the growth of resistant bacteria such as the MRSA.
A thesis submitted to the Department of Biochemistry and Biotechnology, College of Science in partial fulfillment of the requirements for the award of Master of Science Degree in Biotechnology.