Effect of silver nanoparticles on rmtB gene expression in aminoglycoside resistant clinical isolates in Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen that causes widespread infections in hospitals. Pseudomonas aeruginosa has become resistant to a variety of antibiotics due to the overuse of antibiotics. One type of resistance acquired by this bacterium is resistance to aminoglycoside drugs. The most important mechanism of this resistance is the enzymatic inactivation of aminoglycosides by their modifying enzymes. The rmtB gene is involved in this resistance and because silver nanoparticles have antibacterial properties, the present study was conducted to evaluate the expression level of rmtB gene in Pseudomonas aeruginosa specimens treated with silver nanoparticles.

In the current study experimental, 53 samples were collected from 11 laboratories in Mashhad during 1398-1399. Samples were identified using standard laboratory methods and specific culture. PCR method was used to evaluate the frequency of rmtB gene. In order to evaluate the antibiotic susceptibility pattern of the strains, the disk diffusion method based on the CLSI protocol (2018) was used. Silver nanoparticles were made from ginger extract and Real time PCR was used to investigate the effect of silver nanoparticles on rmtB gene expression.

Out of 53 samples of Pseudomonas aeruginosa, 51 samples were resistant to more than two aminoglucosides. Phenotypic evaluation of the antibiotic resistance pattern of aminoglucoside-resistant Pseudomonas aeruginosa strains showed that 61% were resistant to amikacin, 84% to gentamicin and 23% to tobramycin. Also, out of 53 samples, 76% were resistant to all three aminoglycosides. The minimum inhibitory concentration in the agar dilution method for silver nanoparticles was up to 500 μg/ml. Molecular analysis showed the presence of rmtB gene in all samples and the result of real time PCR analysis showed that the effect of silver nanoparticles on rmtB gene expression was significant (P <0.01).

There was high resistance to aminoglycoside in samples collected from Mashhad. Silver nanoparticles had a significant effect on reducing the expression of rmtB gene (P <0.01).