Antibacterial, Anti-Biofilm and Anti-Inflammatory Properties of Azadirachta indica A. Juss (Neem) Oil against Multidrug-Resistant Pathogens

Abstract

Infections caused by the extended-spectrum beta-lactamase (ESBL), Escherichia coli, and methicillin-resistant Staphylococcus aureus (MRSA) pathogens have sparked research on alternative herbal medicines for treatment. This study evaluated the antibacterial, anti-inflammatory, and anti-biofilm properties of Azadirachta indica A. Juss (Neem) oil (NO) against ESBL and MRSA pathogens. Antibacterial activity was assessed through the determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill kinetics to evaluate bacteriostatic/bactericidal effects. The comparative MIC and MBC values obtained for NO against MRSA were 40 \(\mu\)L/mL and 160 \(\mu\)L/mL and for ESBL were 80 \(\mu\)L/mL and 320 \(\mu\)L/mL, respectively. Higher susceptibility of MRSA to NO was indicated by the lower MIC values for MRSA compared to ESBL. Reduction of CFU/ml (Colony forming unit) by NO at 2× MIC was significant compared to NO at ½× MIC.  NO exhibited concentration-dependent biofilm inhibition, with maximum suppression at 25–30 \(\mu\)L/mL, and greater inhibition against Klebsiella than E. coli. In lipopolysaccharide-stimulated mouse macrophages, NO significantly reduced nitric oxide production, and at a 50 \(\mu\)L concentration, the strongest anti-inflammatory effect was exhibited. The findings highlight neem oil as a potential herbal drug for use in antibacterial and anti-inflammatory applications against multidrug-resistant pathogens.