Effect of Iron Oxide Nanoparticles and Probiotic Bifidobacterium bifidum on MexA Gene Expression in Drug Resistant Isolates of Pseudomonas aeruginosa

Pseudomonas aeruginosa (P. aeruginosa), a common cause of nosocomial infections, has an intrinsic resistance to many antibiotics. Among all the multidrug efflux pumps involved in P. aeruginosa drug resistance, MexAB-OprM is the first efflux pump detected to target different classes of antibiotics. The present study aimed to determine the antibacterial effect of iron oxide nanoparticles (IONPs) and probiotic bifidobacterium bifidum (BB) on MexA gene expression, as an important component of the MexAB-OprM multidrug efflux system, in P. aeruginosa isolates of the patients referred to major hospitals in Tehran, between 2018-2017.

In the present descriptive cross-sectional study, a total of 60 isolates of P. aeruginosa were isolated from patients admitted to major hospitals of Tehran, Iran. After bacterial identification via biochemical tests, all strains were evaluated for the presence of MexA of MexAB-OprM multidrug efflux pump in P. aeruginosa using PCR method. After treatment, broth microdilution method and Real-time PCR were used to assess the antimicrobial activity of IONPs and probiotic BB and the gene expression level of MexA component, respectively. Changes in MexA gene expression were analyzed using the -2 ΔΔCT method and independent t-test.

In the present study, 10 isolates (%16.6) of P. aeruginosa harbored MexA gene. The

of MIC testing and gene expression assay showed that IONPs and probiotic BB did not exhibit any inhibitory activity against clinical isolates of P. aeruginosa and no change was observed in MexA gene expression.

Considering the chromosomally encoded MexA, it can be used as markers for identification of drug resistance of P. aeruginosa as essential elements of an effective infection control program. In the viewof the inhibitory activity of IONPs and probiotic Bifidobacterium bifidium on bacterial growth and the low inhibitory effect of the elements on activity of the MexAb-OprM efflux pump, the study of other contributing factors for the development of multi-drug resistance phenotype, including various other efflux pumps and mechanisms influencing maintenance of resistance should not be ignored.