Silver nanoparticles–chitosan composites activity against resistant bacteria: tolerance and biofilm inhibition

Abstract

This study aimed to evaluate the effectiveness of silver nanoparticles–chitosan composites (AgNPs) with different morphologies and particle size distributions against resistant bacteria and biofilm formation. Four different samples were prepared by a two-step procedure using sodium borohydride and ascorbic acid as reducing agents and characterized by UV–Vis absorption spectra, scanning transmission electron microscopy. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the AgNPs were determined according to the Clinical and Laboratory Standards Institute (CLSI) against clinical isolates multidrug-resistant and strains of the American Type Culture Collection (ATCC). An assay was performed to determine the MICs during 20 successive bacteria exposures to AgNPs to investigate whether AgNPs induce tolerance in bacteria. The antibiofilm activities of AgNPs were also evaluated by determining the minimum biofilm inhibitory concentration (MBIC). The spherical AgNPs present diameters ranging from 9.3 to 62.4 nm, and some samples also have rod-, oval-, and triangle-shaped nanoparticles. The MIC and MBC values ranged from 0.8 to 25 μg/mL and 3.1 to 50 μg/mL, respectively. Smaller and spherical AgNPs exhibited the highest activity, but all the AgNPs developed in this study exhibit bactericidal activity. There was no significant MIC increase after 20 passages to the AgNPs. Regarding the antibiofilm activity, MBICs ranged from 12.5 to 50 μg/mL. Again, smaller and spherical nanoparticles presented the best results with phenotypic inhibition of production of slime or exopolysaccharide (EPS) matrix. Thus, it was concluded that AgNPs have a promising potential against resistant bacteria and bacteria that grow on biofilms without inducing tolerance. Supplementary Information The online version contains supplementary material available at 10.1007/s11051-021-05314-1.

Antibacterial and Antibiofilm Potential of Bacterial Cellulose Hydrogel Containing Vancomycin against Multidrug-Resistant Staphylococcus aureus and Staphylococcus epidermidis

“…Santos et al [39], when analyzing the production of the EPS matrix by E. coli, K. pneumoniae, P. aeruginosa, and S. aureus strains through the Congo red method, noticed that after the incorporation of AgNPs into Congo red agar, there was no evident EPS matrix formation, as only red colonies with a mucous texture appeared on the Petri dishes. Therefore, these studies indicate that agents with bactericidal properties, when incorporated into Congo red agar, can reduce both bacterial load and the production of EPS matrix during biofilm formation, as was evidenced in our study, especially after VAN incorporation into HYDROGEL.…”

“…The qualitative determination of the inhibition of the slime production and the exopolysaccharide matrix production was carried out by the Congo red method according to Santos et al [39]. MRSA ATCC 33591 was adjusted in brain heart infusion broth (BHI) to 0.5 on the McFarland scale and incubated at 35 ± 2 • C for 24 h. An aliquot of bacterial growth was then seeded on Congo red agar petri dishes containing HYDROGEL at 0.25%, and VAN and VAN-HYDROGEL at 0.5 × MIC.…”

Saponin-Derived Silver Nanoparticles from Phoenix dactylifera (Ajwa Dates) Exhibit Broad-Spectrum Bioactivities Combating Bacterial Infections

“…The results indicated that AgNPs could prevent biofilm formation, detach biofilm cells, and increase the susceptibility of biofilm cells to antibiotics. A study by [ 89 ] synthesized AgNPs–chitosan composites and assessed their antibiofilm activity against multi-drug-resistant Acinetobacter baumannii . The results suggested that the AgNPs–chitosan composites could inhibit biofilm formation, disrupt biofilm structure, reduce biofilm biomass, and enhance the activity of antibiotics.…”

Gallium–Curcumin Nanoparticle Conjugates as an Antibacterial Agent against Pseudomonas aeruginosa: Synthesis and Characterization

“…Many alternatives to antibiotics have been investigated to fight against P. aeruginosa. − Use of antibacterial nanoparticles is considered to be a promising nonconventional therapy for fighting antibiotic-resistant bacteria owing to its excellent antibacterial activity. − …”