Intracellular, biofilm-inhibitory and membrane-damaging activities of nimbolide isolated from Azadirachta indica A. juss (Maliaceae) against methicillin-resistant Staphylococcus aureus.

This study was designed to evaluate the intracellular killing, membrane-damaging and biofilm-inhibitory activities of nimbolide isolated from Azadirachta indica against MDR MRSA. In vitro antibacterial activity of nimbolide was determined by performing MIC, MBC and time-kill kinetic studies. Bacterial membrane damaging activity was determined by membrane perturbation and Scanning electron microscopy (SEM) examination. Biofilm-inhibitory activities were determined by SEM. Cellular drug accumulation and assessments of intracellular activities were performed using Vero cells culture. SEM revealed that nimbolide caused significant membrane-damage and lysis of the S. aureus cells. The biofilm structure was disrupted and the biofilm formation was greatly reduced in the presence of nimbolide as examined by SEM. The level of accumulation of nimbolide in Vero cells incubated for 24 h is relatively higher than that of ciprofloxacin and nalidixic acid (Cc/Ce for nimbolide > ciprofloxacin and nalidixic acid). The viable number of intracellular S. aureus was decreased (reduction of ~2 log10 c.f.u. (mg Vero cells protein)-1 in a time depended manner in presence of nimbolide (4× MBC) that was comparable to that of tetracycline and nalidixic acid. The significant intracellular, biofilm-inhibitory and bacterial membrane-damaging activities of nimbolide demonstrated here suggested that it has potential as an effective antibacterial agent for the treatment of severe infections caused by MDR...

Source: Journal of Medical Microbiology - August 22, 2016 Category: Microbiology Authors: Sarkar P, Acharyya S, Banerjee A, Patra A, Thankamani K, Koley H, Bag PK Tags: J Med Microbiol Source Type: research