Assessing the effect of exposure to Mangifera indica extract on Staphylococcus aureus antimicrobial susceptibility.

Abstract

BACKGROUND Medicinal plants such as the Mangifera indica have been shown to have activity against bacteria, fungi and viruses and are considered safe which may result underuse or overuse of the herbal products. However overexposure to the extracts of these plants may lead development of antimicrobial resistance to the extract and conventional antibiotics. OBJECTIVES The general objective of this study was to determine the antimicrobial susceptibility of staphylococcus aureus after exposure to Mangifera indica leaf extract. The study tested the hypothesis that Staphylococcus aureus will remain susceptible after exposure to high concentrations of the extract. METHODS Mangifera indica extract was obtained by maceration of 400g of dried pound leaves with 2 liters of 40%V/V ethanol. Susceptibility to the extract, ampicillin and ceftriaxone was carried out using the well diffusion method on Brain heart infusion agar. Staphylococcus aureus (wild type) was then exposed to optimal, suboptimal and supraoptimal concentrations of the extract for 7 days and then recultured from the solutions. The recovered/mutant strain of Staphylococcus aureus was again tested for susceptibility to the extract, ampicillin and ceftriaxone. Diameters of inhibition were used as a measure of susceptibility and compare between the wild type and mutant strain of Staphylococcus aureus. RESULTS The calculated yield of the extract was 11.495% w/w. Qualitative screening revealed presence of tannins, flavonoids, and polyphenols. The MIC of the extract, determined using the graph pad prism was 82mg/ml. Susceptibility of Staphylococcus aureus towards the extract reduced after the 7 day exposure to the extract. A reduction in the susceptibility towards ampicillin was also observed. CONCLUSIONS, STUDY LIMITATIONS AND RECOMMENDATIONS There was a reduction in the susceptibility to the M.indica extract after 7 days of exposure. There was little reduction in the diameters of inhibition to ampicillin on the mutant strain of Staphylococcus aureus which shows potential for cross resistance towards penicillin. However, the study was limited to only Staphylococcus aureus and Mangifera indica herbal extract. Further studies should be carried out in which different bacteria are exposed to Mangifera indica extract or Staphylococcus aureus exposed to other herbal products or a combination of herbal products with antibacterial activity.