Synergism in the Antibacterial Action of Ternary Mixtures Involving Silver Nanoparticles, Chitosan and Antibiotics

Abstract

The investigations of the antibacterial actions, observed in ternary associations involving silver nanoparticles (AgNPs), chitosan and the antibiotics azithromycin (AZ), levofloxacin (LE) or tetracycline (TE), against Gram-negative and Gram-positive bacterial strains, were performed by in vitro antimicrobial susceptibility testing and checkerboard assays. The pH impact in the culture medium was carefully discarded, but preserving the best conditions for solubilizing chitosan. The synergistic antibacterial effects were observed in the most combinations of AgNPs, chitosan and antibiotic, leading to a reduction from 37 to 97% in the minimum inhibitory concentration of the drugs. The mechanisms for the enhanced antimicrobial effects were proposed based on the investigations of the adsorptions of the drugs on the silver surfaces through surface-enhanced Raman scattering (SERS) spectroscopy.

Antimicrobial Actions and Applications of Chitosan

“…However, the antimicrobial effects of pure chitosan and most of its derivatives are still remarkably lower than those of clinical antimicrobial drugs. Several articles have also shown that pure chitosan in combination with clinical drugs exhibits great antimicrobial activity [ 83 , 152 , 199 , 200 , 201 , 202 , 203 ]. Thus, this section focuses on the antimicrobial effects of developed chitosan-based biomaterials with current antibacterial and antifungal drugs because chitosan not only has intrinsic antimicrobial properties but is also able to deliver extrinsic antimicrobial drugs ( Table 3 ).…”

“…Chitosan nanoparticles are synthesized for different purposes by various methods, such as ionotropic gelation, polyelectrolyte complexation, emulsification solvent diffusion, microemulsion, and reverse micelle formation [ 204 , 205 ]. Moreover, the antimicrobial effects of chitosan-based nanoparticles for drug and drug-free delivery systems have been intensively investigated against bacteria and fungi [ 56 , 57 , 58 , 60 , 63 , 67 , 68 , 106 , 119 , 203 , 206 , 207 , 208 , 209 , 210 , 211 , 212 ]. For example, chitosans of different DDAs and MWs exhibited synergistic activity with sulfamethoxazole against P. aeruginosa [ 213 ].…”

Advancements and future directions in the antibacterial wound dressings – A review

“…They found that this ternary material showed a reduction of 97% of the minimum inhibitory concentration of these antibiotics. The proposed mechanism was based on high affinity of chitosan and silver nanoparticles to the bacterial cell wall enabling the release of the adsorbed antibiotics 80 …”

Antibacterial and antibiofilm potential of silver nanoparticles against antibiotic-sensitive and multidrug-resistant Pseudomonas aeruginosa strains

“…Thus, the association of AgNPs with drugs that have an intracellular target is more interesting, as it could provide synergistic effects, than drugs that have an extracellular target [78]. Brasil et al [79] used surface-enhanced Raman scattering spectroscopy (SERS) to assess the association of AgNPs, chitosan, and the antibiotics azithromycin, levofloxacin, or tetracycline against Gram-negative and Gram-positive bacteria strains, noting that the combination promoted a reduction of 37-97% in the minimum inhibitory concentration of drugs. Deng et al [80] observed the interaction of AgNPs with the antibiotics enoxacin, neomycin and tetracycline, showing through Raman's technique that they form complex with AgNPs and may exhibit a synergistic effect against microorganisms.…”