ANTIBACTERIAL ACTIVITY OF PSIDIUM GUAJAVA LINN. STEM BARK EXTRACTS ON MULTI DRUG RESISTANT (MDR) COMMUNITY ACQUIRED METHICILLIN-RESISTANT STAPHYLOCOCCUS AUREUS (CA-MRSA)

BACKGROUND: medicinal plants are rich in a numerous variety of secondary metabolites of antimicrobial properties. Psidium guajava is one of the parts in folk medicine that has been used for the management of various disease conditions and is believed to be active. As a consequence of the intense fight against infections, bacteria have evolved through numerous defenses against antimicrobial agents. OBJECTIVE: to determine the inhibitory effect of P guajava Linn. stem bark extracts on multidrug resistant methicillin-resistant Staphylococcus aureus’isolates. MATERIALS AND METHODS: Stock cultures of 51 Staphylococcus aureus’isolated from healthy individuals maintained on nutrient agar slants at 4°C were used for this study. The disc diffusion method was used to determine the resistance of the Staphylococcus aureus isolates to methicillin (oxacillin) and to other conventional antibiotic susceptibility discs using standard concentration. The plant materials were extracted and phytochemicals quantified using standard techniques. The agar well diffusion procedure was used for the assessment of the sensitivity of the extracts. RESULTS: nine isolates were resistant to at least 4 of the antibiotics used. The mean inhibition zone diameter (IZD) of the extracts ranged from 10-16 mm with ethanolic extracts exhibiting higher activities. Five isolates showed complete resistance to Psidium guajava extracts. Inhibitory activities of both water and ethanolic extracts were distributed across 4 isolates with organism E14 showing maximum susceptibility profile. The phytochemicals estimated in mg/g dry body weight included: total phenol (111.86±0.47), tannin (141.92±0.51), flavonoids (3.37±0.04), vitamin C (1.67±0.03), saponin (285.76±0.81), and alkaloid (111.065±0.38). The extracts of Psidium guajava stem bark though showed high phytochemical contents have relatively low inhibitory activity on the multidrug resistant (MDR) community acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) isolates. CONCLUSION: the results of this study demand the introduction of antimicrobials with novel modes of action.