Broad-spectrum antibacterial and antibiofilm activity of biogenic silver nanoparticles synthesized from leaf extract of Phyllanthus niruri

Abstract

Multidrug resistance (MDR) among pathogenic bacteria is a global health concern as it has rendered the current antibiotic therapy ineffective. A recent and rapidly developing research area in the biomedical sector is the use of biogenic nanoparticles as antibacterial agents. In the current investigation, aqueous leaf extract of Phyllanthus niruri (Pn-AgNPs) were employed for the biogenic synthesis of silver nanoparticles, further characterized by SEM, EDX, FTIR, TEM, UV-Vis and XRD techniques. Electron microscopy images of the green-synthesized Pn-AgNPs showed them as evenly dispersed spherical particles having an average size of about ∼20 nm. The Pn-AgNPs were further tested for potential antibacterial activity against isolated drug-resistant pathogenic bacteria such as Burkholderia cepacia complex, carbapenem-resistant Enterobacterales (CRE), Citrobacter freundii, Enterococcus faecalis, Escherichia coli, Enterobacter clocae, MRSA, Salmonella typhi, Streptococcus spp, and vancomycin-resistant Enterococci (VRE).The Pn-AgNPs significantly inhibited growth all of the studied bacterial isolates, including antibiotic-resistant isolates such as MRSA, VRE, and CRE. Electron micrographs clearly showed the enhanced penetration of AgNPs leading to disruption of cell membrane causing death of the cell. Further, Pn-AgNPs dramatically reduced the ability of P. aeruginosa, Bacillus cereus, E. coli, and S. aureus to form biofilms. Leakage of protein from bacterial cells could be main reason for the effective bactericidal action of synthesized AgNPs. This antibacterial and antibiofilm potential of Phyllanthus niruri biosynthesized AgNPs against clinically significant drug-resistant bacteria is impressive and can be developed as a novel antimicrobial agent to combat the threat of drug-resistant bacterial infections.