Evaluation of inhibitory potential of locally found plants in North-EasternIndia on clinically isolated pathogens

Plant extracts are a valuable source of novel antibacterial compounds to combat pathogenic isolates. Increasing concern for antimicrobial resistance in infectious agents and antibiotic side-effects makes it mandatory to search for alternatives with greater efficacy and lesser side effects. The aim of the study was to evaluate in vitro bactericidal activity of five locally found plants, in dependence on time and concentration against clinical isolates of multidrugresistant bacteria. Plant material (F. geniculata (leaves), B. diffusa (whole plant), M. indica (seed), P. pinnata (seed) and C. tora (leaves)) were extracted and dissolved in methanol for its further antibacterial evaluation. Bacterial strains were isolated form clinical samples (E. coli, K. pneumonia, P. aeruginosa and S. aureus). Minimum inhibitory concentration (MIC) for each plant extract was measured by broth dilution method. Time-kill assay was carried out at doses equivalent of MIC/2, MIC and MICx2, to estimate changes in the growth curve of investigated pathogens. Percentage inhibition was monitored for all four examined microorganisms. Minimum inhibitory concentration recorded variably ranging between 1 – 6 mg/ml for all five plant extracts. Suppressed growth of E. coli and S. aureus was recorded during complete period of investigation i.e. at 0, 2, 4, 6, 24 h by all plant extracts except for Madhuca indica seed extract which showed strong microbial inhibitory potential against S. aureus but was weak against other pathogens. P. aeruginosa was not very susceptible to any of the extracts. It was evident from the study that methanolic extract of all five plants posses antimicrobial activity.