AUTHOR=Loo Yuet Ying , Rukayadi Yaya , Nor-Khaizura Mahmud-Ab-Rashid , Kuan Chee Hao , Chieng Buong Woei , Nishibuchi Mitsuaki , Radu Son 

TITLE=In Vitro Antimicrobial Activity of Green Synthesized Silver Nanoparticles Against Selected Gram-negative Foodborne Pathogens

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.01555

DOI=10.3389/fmicb.2018.01555

ISSN=1664-302X

ABSTRACT=<p>Silver nanoparticles (AgNPs) used in this study were synthesized using pu-erh tea leaves extract with particle size of 4.06 nm. The antibacterial activity of green synthesized AgNPs against a diverse range of Gram-negative foodborne pathogens was determined using disk diffusion method, resazurin microtitre-plate assay (minimum inhibitory concentration, MIC), and minimum bactericidal concentration test (MBC). The MIC and MBC of AgNPs against <italic>Escherichia coli</italic>, <italic>Klebsiella pneumoniae</italic>, <italic>Salmonella</italic> Typhimurium, and <italic>Salmonella</italic> Enteritidis were 7.8, 3.9, 3.9, 3.9 and 7.8, 3.9, 7.8, 3.9 μg/mL, respectively. Time-kill curves were used to evaluate the concentration between MIC and bactericidal activity of AgNPs at concentrations ranging from 0×MIC to 8×MIC. The killing activity of AgNPs was fast acting against all the Gram-negative bacteria tested; the reduction in the number of CFU mL<sup>-1</sup> was &gt;3 Log<sub>10</sub> units (99.9%) in 1–2 h. This study indicates that AgNPs exhibit a strong antimicrobial activity and thus might be developed as a new type of antimicrobial agents for the treatment of bacterial infection including multidrug resistant bacterial infection.</p>