SUSCEPTIBILITY STUDIES OF SOME FOOD BORNE PATHOGENS TO GROWTH INHIBITORY COMPONENTS OF MANGIFERA INDICA (BARK), KHAYA SENEGALENSIS (ROOT/STEM BARK) AND SECURIDACA LONGIPEDUNCULATA (ROOT-BARK)

Abstract

Medicinal plants represent a rich source of antimicrobial agents. In this study, the susceptibility pattern of Staphylococcus aureus, Escherichia coli 0157.H7, Pseudomonas aeruginosa, Klebsiella sp. and Aspergillus flavus to the bioactive compounds in extracts of Khaya senegalensis, Mangifera indica and Securidaca longipedunculata were assayed using agar well diffusion method. The Minimum Inhibitory Concentration (MIC) of the plant extracts were also determined using standard methods. Zones of growth inhibition of the test organisms to methanol and aqueous extracts of test plants was used to ascertain susceptibility and it ranged from 8 – 30 mm (met) and 0 – 22 mm (aq) for K. senegalensis, 10 – 28 mm (met) and 0 – 23 mm (aq) for M. indica as well as 0 – 20 mm (met) and 3 – 20 mm (aq) for S. longipedunculata. S. aureus was the most susceptible to all three plant extracts with highest zone of inhibition of 30 mm in methanol extract of K. senegalensis and 23 mm to aqueous extract of M. indica. E. coli 0157 was most susceptible to K. senegalensis with 23 mm (met) and 22 mm (aq) but showed total resistance to aqueous extracts of S. longipedunculata. The fungus, A. flavus exhibited highest susceptibility to extracts of K. senegalensis with 23 mm (met) and 18 mm (aq) but was least sensitive to S. longipedunculata. P. aeruginosa was the least susceptible to extracts of all test plants. MIC of test plants ranged from 25 mg/ml – 100 mg/ml with K. senegalensis most effective at low concentration. All test organisms were more susceptible to plant extracts assayed than the conventional antibiotics normally used to treat infections caused by them. This suggests a great potential of these plants as new sources of more effective antimicrobial agents.