Pathogens in exacerbations of chronic rhinosinusitis differ in sensitivity to silver nanoparticles

PurposeThe significance of the microbiome in chronic rhinosinusitis (CRS) is not clear. Antimicrobials are recommended in acute exacerbations of the disease (AECRS). Increasing rates of antibiotic resistance stimulate research on alternative therapeutic options including silver nanoparticles (AgNPs), sometimes referred to as "colloidal silver". However, there are concerns regarding the safety of silver administration and the emergence of silver resistance. The aim of this cross-sectional observational study was to assess the sensitivity of sinonasal pathogens to AgNPs and compare it with the toxicity of AgNPs for nasal epithelial cells. MethodsNegatively charged AgNPs (12{+/-}5 nm) were synthetized using tannic acid. The minimal inhibitory concentration (MIC) for pathogens isolated from patients with AECRS was approximated. Cytotoxicity of AgNPs was tested in vitro on human nasal epithelial cells line. Results48 clinical isolates and 4 reference strains were included in the study (Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Acinetobacter baumanii, Serratia marcescens, Enterobacter cloacae). The MIC values differed between isolates, even within the same species. All the isolates (including antibiotic resistant) were sensitive to AgNPs in concentrations nontoxic to human cells during 24 h exposition. However, 48 h exposition to AgNPs increased toxicity to human cells, narrowing their therapeutic window and enabling 19% of pathogens to resist the AgNPs biocidal action. ConclusionsAgNPs are effective against most pathogens isolated from patients with AECRS, but sensitivity testing may be necessary before application. Results of sensitivity testing for reference strains cannot be extrapolated to other strains of the same species.