E. coli ST131 enfeksiyonlarının tedavisinde yeni bir yaklaşım: Nano taşıyıcı ile hedefe yönlendirilmiş antimikrobiyal ajanlar

Escherichia coli (E.coli) ST131 is a globally disseminating high risk clone associated with multidrug resistance and failure of antimicrobial therapy. There is an urgent need for alternative approaches to treat E.coli ST131 infections. Our aim was to design a SPION (Super Paramagnetic Iron Oxide Nanoparticle) based drug delivery system targeting E.coli ST131 clone. In this study, we studied on a quinolone resistant uropathogenic E.coli ST131 isolate to assess the efficacy of targeted delivery system. Polyacrylic acid (PAA) coated SPIONs were synthesized by dissolving FeCl2 and FeCl3 salts in deoxygenated water and coating SPIONs with PAA. Nanoparticle size was 33.2 nm. After characterization of the particles regarding hydrodynamic and crystal size, zeta potential for surface charge and stability, SPIONs were conjugated with mannoside analog (4-aminophenyl α-D-mannopyranoside) to target fimH adhesin of E.coli ST131. Subsequently, ciprofloxacin was attached to the SPION-Mannoside complex. Specific interaction and antibacterial activity of delivery system were examined on planktonic and sessile cells of E.coli ST131 isolate by using growth inhibition, confocal imaging, and scanning electron microscopy (SEM) techniques. Furthermore, photothermal therapy (PTT) was applied at power of 1150 mW for ten minutes in combination with SPION exposure. SPIONs at 25 μg/ml concentration (alone or conjugated with mannoside) did not cause significant growth inhibition both on planktonic and sessile cells of E.coli ST131. The mean colony count of E.coli ST131 planktonic cells after incubation with SPION and SPION-Mannoside were 2.26x1012 and 9.89x1011 CFU/ml, respectively while it was 1.22x1012 CFU/ml in control culture. In biofilm, incubation with mannoside conjugated 25 μg/ml SPION resulted in 1.55x1010 CFU/ml mean colony count while SPION and control cultures revealed 2.04x1010 CFU/ml and 7.76x109 CFU/ml bacterial growth, respectively. Confocal microscopy indicated more specific and enhanced attachment of SPION-Mannoside particles to the surface of E.coli ST131 compared to SPION alone. However, the SPION particles were seen accumulated on biofilm surface and did not penetrate inside the biofilm matrix. After conjugation of ciprofloxacin to SPION-mannoside, the delivery system did not cause a significant reduction in growth of planktonic and sessile cells (log change in mean CFU/ml lower than 2-log). The mean colony counts of planktonic cells were 1.70x1010 and 4.32x1012 CFU/ml at ciprofloxacin-mannoside conjugated SPION and control cultures, respectively. In biofilm, incubation with ciprofloxacin-mannoside conjugated SPION resulted in growth of 1.66x1010 CFU/ml mean colony count while it was 3.24x1010 CFU/ml for control. PTT application did not enhance the efficiency of delivery system. No significant decrease in bacterial growth was observed. SPION based targeted therapy is a unique and promising approach to treat persistent E.coli ST131 infections. Our future goals are to integrate quinolone derivatives and efflux pump inhibitors to our mannoside conjugated SPION cargo system.