الفهرس 
Introduction & Aim of the studyOnly 14 pages are availabe for public view
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Abstract
P. aeruginosa is one of the ESKAPE pathogens capable of escaping the bacteriocidal activity of various groups of antimicrobials.
Worldwide, P. aeruginosa is known as a major nosocomial pathogen. In Egypt, MDR P. aeruginosa had emerged and present mainly in nosocomial infections due to overusage of antibiotics. Therefore, a new class of antimicrobial agents with a completely different structure and mode of action is urgently needed.
Recently, Nanoparticles have been attracting interest for treating different diseases, including those caused by bacterial infections. Increased therapeutic efficacy against a numerous of bacterial infections, involving P. aeruginosa has been documented.
The current study was done to detect the prevalence of MDR P. aeruginosa strains, their resistance pattern, antibacterial activity of TDN alone and in conjugation with the traditional antibiotics against MDR P.aeruginosa isolates, phenotypic detection of efflux pump and biofilm production of the isolated strains, evaluate the ability of titanium dioxide nanoparticles to inhibit biofilm production and effect of it on the gene expression of quorum sensing and efflux pump.
In this study, Titanium dioxide nanoparticles were formed by sol gel method, characterized by DLS, HR-TEM, DSC, FTIR, X- ray. The particle size of Titanium dioxide nanoparticles (TDN) were 64.77 ± 0.14 nm with homogenous distribution of particle size (PDI value <0.3). HR TEM of TDN revealed that the particles were irregular circular.
Data of FTIR, DSC and X- ray confirmed the formation of TDN and confirmed the absence of interaction between TDN and used antibiotics.
Out of 100 different clinical specimens, 67 P. aeruginosa strains were recovered. P. aeruginosa isolates were mainly separated from ear discharge samples (100%), followed by urine samples (78%), wound exudates (66.7%), eye discharge (40%), sputum specimens (20%). while no P. aeruginosa isolates were recovered from burn swabs specimens.
Resistance pattern of isolated P. aeruginosa strains were determined by using disc diffusion method. P. aeruginosa strains were high resistance to Ceftriaxone (89.5%), followed by Cefepime (59.7%), Amikacin, (31.34%), Imipenem (29.8%), Ciprofloxacin (25.4%), and the least resistance to Levofloxacin (12%).
We chose 25 P. aeruginosa isolates that were multi drug resistance with various antibiotic resistance patterns and recovered from different clinical specimens.
Antibacterial activity of TDN was detected against the chosen isolates of P.aeruginosa. Titanium dioxide nanoparticles (TDN) had excellent antimicrobial activity compared to Titanium dioxide bulk form (TDP). As titanium dioxide nanoparticles have MICs ranging from 8 to 64 μg /ml, and 3 isolates were sensitive to it (MIC less than 1 μg /ml).
The combination effects between Titanium dioxide nanoparticles (TDN) and the used drugs were detected against the chosen isolates of P. aeruginosa by Checkerboard assay.
When antibiotics are conjugated with TDN, their MICs are reduced significantly against the chosen P. aeruginosa isolates. This phenomen named synergistic effect. The conjugation of nanoparticles and Cefepime had synergistic effect against all selected strains (100%), then Ceftriaxone (96%), Amikacin (88%), Ciprofloxacin (80%) and Meropenem (60%).
In this study, phenotypic detection of efflux pump system in 25 MDR P. aeruginosa was occurred by using CCCP. Active efflux pump were detected when MICs of the tested antibiotics decrease 4-fold or more in the presence of CCCP.
Amikacin is effluxed by 25 MDR P. aeruginosa isolates (100%). For Meropenem, Ceftriaxone and Ciprofloxacin only 80 %, 80%, 79% of isolates showed 4 fold reductions or more in MICs in presence of CCCP. These results suggest that active efflux pumps are included in the antibiotics resistance of MDR P. aeruginosa isolates.
In vitro biofilm development results showed that 44% of MDR P. aeruginosa isolates were high biofilm producers, 28% were moderate biofilm producers and 28% were non or weak biofilm producers. TDN showed a significant inhibitory effect on biofilm production (96%) of 25 MDR P. aeruginosa isolates.
In molecular level, TDN suppresses expression of efflux pump gens (MexY, MexB, and MexA) and quorum sensing regulated genes (lasR,rhlR, lasI, pqsA, pqsR and rhll). While occur slight upregulation to oprM gene.