title: Combined efficacy of biologically synthesized silver nanoparticles and different antibiotics against multidrug-resistant bacteria.
abstract: Biological synthesis of nanoparticles is a growing innovative approach that is relatively cheaper and more environmentally friendly than current physicochemical processes. Among various microorganisms, fungi have been found to be comparatively more efficient in the synthesis of nanomaterials. In this research work, extracellular mycosynthesis of silver nanoparticles (AgNPs) was probed by reacting the precursor salt of silver nitrate (AgNO3) with culture filtrate of Aspergillus flavus. Initially, the mycosynthesis was regularly monitored by ultraviolet-visible spectroscopy, which showed AgNP peaks of around 400-470 nm. X-ray diffraction spectra revealed peaks of different intensities with respect to angle of diffractions (2θ) corresponding to varying configurations of AgNPs. Transmission electron micrographs further confirmed the formation of AgNPs in size ranging from 5-30 nm. Combined and individual antibacterial activities of the five conventional antibiotics and AgNPs were investigated against eight different multidrug-resistant bacterial species using the Kirby-Bauer disk-diffusion method. The decreasing order of antibacterial activity (zone of inhibition in mm) of antibiotics, AgNPs, and their conjugates against bacterial group (average) was; ciprofloxacin + AgNPs (23) . imipenem + AgNPs (21) > gentamycin + AgNPs (19) > vancomycin + AgNPs (16) > AgNPs (15) . imipenem (14) > trimethoprim + AgNPs (14) > ciprofloxacin (13) > gentamycin (11) > vancomycin (4) > trimethoprim (0). Overall, the synergistic effect of antibiotics and nanoparticles resulted in a 0.2-7.0 (average, 2.8) fold-area increase in antibacterial activity, which clearly revealed that nanoparticles can be effectively used in combination with antibiotics in order to improve their efficacy against various pathogenic microbes.
authors.affiliation: Microbiology Research Laboratory, Department of Microbiology, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan.
authors.forename: Syed Zeeshan Haider
authors.initials: SZ
authors.lastname: Naqvi
authors.forename: Urooj
authors.initials: U
authors.lastname: Kiran
authors.forename: Muhammad Ishtiaq
authors.initials: MI
authors.lastname: Ali
authors.forename: Asif
authors.initials: A
authors.lastname: Jamal
authors.forename: Abdul
authors.initials: A
authors.lastname: Hameed
authors.forename: Safia
authors.initials: S
authors.lastname: Ahmed
authors.forename: Naeem
authors.initials: N
authors.lastname: Ali
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology*; D001231:Aspergillus flavus / Q000378:metabolism; D001419:Bacteria / Q000187:drug effects*; D052978:Disk Diffusion Antimicrobial Tests; D024901:Drug Resistance, Multiple, Bacterial / Q000187:drug effects*; D053768:Metal Nanoparticles / Q000737:chemistry*; D012834:Silver / Q000737:chemistry / Q000494:pharmacology*; D012835:Silver Nitrate / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D012834:Silver; D012835:Silver Nitrate
keywords: Aspergillus flavus; antibacterial agents; mycosynthesis; silver nanoparticles