Pseudomonas aeruginosa is an opportunistic bacterium that, mainly through the alginate biofilm formation, can cause sever and chronic lung infetions in the respiratory tracts of cystic fibrosis patients they can rarely be removed by antibiotic usage alone. The main objective of this project was to investigate synergistic effects tobramycin and cefixime with alginate lyase whether degradation of alginate by alginate lyase would increase antibiofilm efficacy of tobramycin and cefixime on mucoid strain of P. aeruginosa biofilm. In order to purify alginate lyase enzyme and its effect on biofilm elimination, the alginate lyase (algL) gene was isolated from mucoid strain of P. aeruginosa TAG48, cloned, sequenced and expressed in E. coli. The resultant enzyme was purified by affinity chromatography. The of tobramycin and cefixime were also used to test the effectiveness of these antibiotics on biofilm as well as planktonic cells of P. aeruginosa by carrying out Minimum Inhibitory Concentration (MIC), Minimum Biofilm Inhibitory Concentration (MBIC), and Minimum Biofilm Eradication Concentration (MBEC). The synergistic effects of these antibiotics and the recombinant alginate lyase enzyme on biofilm and planktonic cells were evaluated. Results from the antimicrobial characteristics of the antibiotics and the enzyme have shown MIC for tobramycin, cefixime and enzyme in the following concentrations: 4, 16,128 and 9.37 μg/ml, respectively, MBIC: 4, 32, 256 and 18.75 μg/ml, respectively, and MBEC: 32, 128, ≥ 512 and 37.5 μg/ml, respectively. The study of synergism between the antibiotics and the enzyme to prevent growth and eradicate planktonic cells as well as the biofilm of P. aeruginosa TAG48 show that alginate lyase exhibits synergy with tobramycin and cefixime. In conclusion, results support that alginate plays a significant role in P. aeruginosa biofilm and combination of antibiotis with alginate lyase, which degrades the alginate, might benefit treating patients by increa
