Investigation of the synergistic effects of the extract of neem with conventional antibiotic against gram positive and gram negative microorganism

Abstract

Background: Nowadays, several antibiotics used for the treatment of a variety of infectious human diseases possess a limited antimicrobial spectrum due to the emergence of multi drug-resistant (MDR) bacterial strains. It has therefore lead to the use of two or more antimicrobial agents as a combination treatment for preventing or delaying the emergence of resistant microbial strains and in certain cases also exhibits a synergistic effect which proves useful in the treatment of bacterial infections especially in otherwise resistant-bacteria cases. Neem, a traditionally known plant in the Indian system of medicine is a worldwide recognized natural antibiotic. Thus, in the present investigation an attempt has been made to study the effect of use of Neem extract along with several antibiotics as a combination to overcome the occurrence of resistance. Methods and materials: The alcoholic extract of Neem leaves was used for the study. Solution A containing Neem extract 5 mg/mL alone, Solution B comprising of Standard antibiotics alone 5 mg/mL and Solution C containing combination of 2.5 mg/mL of Neem extract and selected standard antibiotic at a concentration of 2.5 mg/mL were tested for their antibacterial potential against selected strain of micro-organisms namely Klebsiella pneumoniae, Staphylococcous aureus, Pseudomonas aeruginosa, E. coli and Bacillus subtilis using agar plate technique. Results: The antimicrobial activity was assessed by measuring the diameter of zone of inhibition. The results indicated the synergistic activity exhibited by the combination of Neem extracts and half the concentration of the standard antibiotics used in the study. Thus, the dose of standard antibiotics may be reduced to almost half in concentration when combined with the Neem extract without compromising the efficacy. The use of natural antibiotic thus helps to achieve reduction in dose of standard antibiotic. Conclusion: The zone of inhibition observed were almost comparable thus the combination of neem extract and antibiotic will help to reduce the dose of standard antibiotics, thereby preventing occurrence of drug resistance. Finally it can be concluded from the research of neem extract with conventional antibiotics and their combination with antibiotic/neem extract can be used as novel antimicrobial agent against multidrug resistance pathogenic microorganism.