Abstract
Most of the infections caused by multi-drug resistant (MDR) P. aeruginosa strains are extremely difficult to be treated with conventional antibiotics. Biofilm formation and efflux pumps are recognized as the major antibiotic resistance mechanisms in MDR P. aeruginosa. Biofilm formation by P. aeruginosa depends mainly on the cell-to-cell communication quorum-sensing (QS) systems. Titanium dioxide nanoparticles (TDN) have been used as antimicrobial agents against several microorganisms but have not been reported as an anti-QS agent. This study aims to evaluate the impact of titanium dioxide nanoparticles (TDN) on QS and efflux pump genes expression in MDR P. aeruginosa isolates. The antimicrobial susceptibility of 25 P. aeruginosa isolates were performed by Kirby–Bauer disc diffusion. Titanium dioxide nanoparticles (TDN) were prepared by the sol gel method and characterized by different techniques (DLS, HR-TEM, XRD, and FTIR). The expression of efflux pumps in the MDR isolates was detected by the determination of MICs of different antibiotics in the presence and absence of carbonyl cyanide m-chlorophenylhydrazone (CCCP). Biofilm formation and the antibiofilm activity of TDN were determined using the tissue culture plate method. The effects of TDN on the expression of QS genes and efflux pump genes were tested using real-time polymerase chain reaction (RT-PCR). The average size of the TDNs was 64.77 nm. It was found that TDN showed a significant reduction in biofilm formation (96%) and represented superior antibacterial activity against P. aeruginosa strains in comparison to titanium dioxide powder. In addition, the use of TDN alone or in combination with antibiotics resulted in significant downregulation of the efflux pump genes (MexY, MexB, MexA) and QS-regulated genes (lasR, lasI, rhll, rhlR, pqsA, pqsR) in comparison to the untreated isolate. TDN can increase the therapeutic efficacy of traditional antibiotics by affecting efflux pump expression and quorum-sensing genes controlling biofilm production.
Highlights
This study aims to evaluate the impact of titanium dioxide nanoparticles (TDN) on the activity of the tested antimicrobials, QS and efflux pump genes expression in multidrug resistant (MDR) P. aeruginosa isolates
Twenty-five P. aeruginosa isolates were recovered from different clinical specimens, including three ear discharge specimens, thirteen urine, and nine wound exudate samples
The antimicrobial susceptibility of P. aeruginosa strains was detected by using the Kirby–Bauer disk diffusion method according to criteria provided by the Clinical & Laboratory
Summary
According to the World Health Organization (WHO), P. aeruginosa is one of the most virulent and resistant bacteria for which new antimicrobials are urgently needed [1]. P. aeruginosa is characterized by bacterial resistance syndrome, as most recognized antimicrobial resistance pathways can be found in this strain [2]. One of the important mechanisms of antibiotic resistance in P. aeruginosa is the exclusion of antibiotics through multidrug resistance (MDR) efflux systems, especially those that belong to the resistance-nodulation-division (RND) family. MexAB-OprM, MexXY and MexCD-OprJ are considered the main cause of intrinsic and acquired multidrug resistance [3]
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