Synergistic effects of neem (Azadirachta indica L.) leaves extract with conventional antibiotic against gram positive and negative microorganism

Abstract

Background: Neem has been known to possess several complex phytoconstituent(s) and exhibits wide array of medicinal and household uses that are attributed to its active isolate(s) that possesses an ability to cure many chronic disease(s) and disorder(s). The current investigation aimed to study the combined antimicrobial effect of crude Neem extract and selected antibiotics namely Ciprofloxacin, Cefixime, Chloramphenicol, Ampicillin, Sulfamethoxazole, Tetracycline and Ofloxacin on selected Gram’s positive and negative micro organism. Crude alcoholic Neem leaf extract was used for the study.
 Method: Solution A containing Neem extract 5 mg mL-1 alone, Solution B comprising of Standard antibiotics alone 5 mg mL-1 and Solution C containing combination of 2.5 mg mL-1 of Neem extract and selected standard antibiotic at a concentration of 2.5 mg mL-1 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 obtained results indicated the synergistic activity of the Neem extract and the selected antibiotics. It was observed that half concentration of antibiotic was sufficient to exert the antimicrobial effect when they were combined with Neem extract. Thus, the dose of standard antibiotics may be marginally reduced to almost half in concentration when combined with the Neem extract without compromising the efficacy. The zones of inhibition indicated that the combination of Neem extract and antibiotic exerted a synergistic effect which will facilitate to achieve reduction of the dose of standard antibiotics.
 Conclusions: It can be concluded from the research that Neem extract when combined with the conventional antibiotic(s) can be used as a novel antimicrobial agent which exhibits a synergistic effect and also helpful to achieve a dose reduction of conventional antibiotic(s).