Effect of silver and chitosan nanoparticles on gentamicin and ciprofloxacin resistance and expression of MexAB-OprM and AdeABC efflux pumps in multi drug resistant Pseudomonas aeroginosa and Acinetobacter baumannii

Abstract

The aim of this study was to evaluate the antibacterial activity of silver and chitosan nanoparticles (NPs) alone and in combination with either ciprofloxacin or gentamicin against A.baumannii and P.aeruginosa isolates and the efficacy of them to alter the expression level of efflux pumps and also any increase in the inhibitory capacity of antibiotics against A.baumannii and P.aeruginosa.

Method: The antibacterial activities of Ag NPs, and its combination to ciprofloxacin (ANC) and gentamicin (ANG) and also chitosan, chitosan NPs and its combination to ciprofloxacin (CNC) and gentamicin (CNG) were evaluated through the use of micro dilution broth, disc diffusion and drop diffusion methods. In addition, the toxicity of the synthesized materials was calculated by MTT assay. To conduct the experiments of the expression of target genes of mexB, mexY, abeM and adeB, initially antibiotic resistant A. baumannii and P. aeruginosa (PAO1) strains were exposed to the synthetic substances in their sub inhibitory levels then RNA was extracted to study the antibacterial effects of the nanoparticles in relation to the expression of the efflux pump using real-time PCR.

Results: The result showed because of the difficulty of movement of the synthetic substances on the Agar medium, antibacterial activities of Ag NPs, chitosan NPs, ANG, ANC ,CNC,CNG and Chitosan against P.aeruginosa and A.baumannii were not the same using three analytic methods, namely disk diffusion method, drop diffusion method and micro dilution broth. So that micro dilution broth was the most amenable technique among the three procedure. In addition MTT assay showed nanoparticles and their combination with antibiotics have toxic properties on stem cells. However, chitosan and its nanoparticle forms combined with antibiotics, did not show toxic properties on stem cells. The result also showed efflux pump expression of adeB and abeM in A.baumannii, mexB and mexY in P. aeruginosa decreased after treating them with chitosan, chitosan nanoparticle and silver nanoparticle, so they are good candidate as an efflux pump inhibitor in research projects. However, increased resistance to ciprofloxacin and gentamicin antibiotics was observed after exposure to nanoparticles.