Antibacterial and antibiotic potentiating activity of Vangueria madagascariensis leaves and ripe fruit pericarp against human pathogenic clinical bacterial isolates

This study aimed to assess the antibacterial and antibiotic potentiating property of Vangueria madagascariensis (VM) (fruit and leaf extracts) against 10 clinical isolates. A microdilution broth susceptibility assay for bacteria was used for the determination of the minimum inhibitory concentration (MIC) and associated with antibiotics to evaluate any synergistic effect. VM extracts were found to potentiate the activity of 3 conventional antibiotics. Chloramphenicol and Ciprofloxacin showed no activity against Acinetobacter spp. but when mixed with VM (in a ratio of 50% VM extracts: 30% antibiotic), showed potentiating effect. The methanolic fruit extract at lower concentration of Chloramphenicol (30%) gave better synergistic effect (MIC = 3.75 μg/mL) as compared to 50% (MIC = 12.5 μg/mL). With Gentamicin, no activity was detected with leaf decoction but other extracts (methanolic leaf/fruit extract and fruit decoction) showed enhancement (MIC- 0.47, 7.5 and 15 μg/mL respectively). Interestingly, Chloramphenicol showed no activity against MRSA, but when mixed with VM, produced low MICs (<0.39-0.78 μg/mL with 50% antibiotic and from <0.47 to 0.94 μg/mL with 30% antibiotic). Combining Gentamicin with VM extracts showed an enhancement in the potentiating activity against MRSA. In conclusion, the observed antimicrobial property of VM tend to suggest a promising alternative and complementary strategy to manage bacterial infections and hence can open new avenues for further research using traditional medicinal food plant.