Abstract
A rising number of hospital infections were caused by multi drug resistant A.baumannii. This microorganism has become a big global concern for clinicians. This study aimed to evaluate the antimicrobial activity of biosynthesized TiO2 nanoparticles against biofilm producing multi drug resistant A. baumannii. Bacteria were isolated from burn wounds. The selected isolate was identified using the routine biochemical assays, viteck 2, and confirmed by PCR technique, targeting the 16S rRNA and blaOXA-51 genes. Antimicrobial susceptibility tests were performed using Viteck 2 system and the biofilm production was tested by using microtiter plate method. S marcescens was used for production of the prodigiosin which characterized later by UV-visible spectroscopy and then was used for biosynthesis of titanium dioxide nanoparticles (TiO2) NPs. Atomic force microscopy, X-ray diffractometer and field emission scanning electron microscopy were used for characterization of TiO2 NPs. Antimicrobial activity of TiO2 NPs was examined by well diffusion assay using concentration of 0.4- 0.006 mg/ml. The studied isolate was beta-lactamase producer and showed resistance to aminoglycosides, quinolones, furanes and trimethoprim/ sulphonamide, PCR amplification of 16S rRNA and blaOXA-51 genes was used for detection of A baumannii. The selected isolate was a strong biofilm producer with 5.9 times more than the OD values of the control. Atomic force microscopy images showed that the synthesized TiO2 NPs were in spherical shape with an average diameter of 67.49 nm. The TiO2 NPs inhibited the bacterial growth at concentrations of ≥ 0.1mg/ ml and a maximum zone of inhibition recorded was 22 mm at concentration of 0.4 mg/ ml. Biosynthesis of TiO2 NPs using prodigiosin was showed a promising antibacterial activity against strong biofilm producing MDR- A. baumannii.

Key words: A. baumannii, Antimicrobial activity, Biofilm, Prodigiosin, TiO2 nanoparticles.