Antibacterial effect of neem (azadirachta indica) oil on multidrug resistant bacteria isolated from human infections

Abstract

Abstract Aim: The aim of the present study was to determine the inhibitory and killing effect of neem (Azadirachta indica) oil on multidrug resistant bacteria isolated from human infections. Methods: Twenty five strains of multidrug resistant Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa isolated from different clinical specimens were used in the study. Time kill assay and broth macrodilution methods for determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were used to study the inhibitory and bactericidal effect of neem oil on these multidrug resistant bacteria. Results: Undiluted neem oil killed all strains of S. aureus within 8 h of exposure, whereas neem oil at concentration 500 µl/ml took 18 h to kill S. aureus. Undiluted neem oil killed E. coli and P.aeruginosa within 18 h of exposure. The MIC of neem oil was 500 µl/ml. Conclusion: Neem oil showed bactericidal effect on both gram-positive (S. aureus) and gram negative (E. coli and P. aeruginosa) bacteria. The anti-bacterial effect of neem oil was concentration and time dependent. S. aureus was more susceptible to neem oil than E. coli and P. aeruginosa.