Phage Therapy as an Alternative Way for Treatment of Colistin-resistant Acinetobacter baumannii

Background and Objectives: Acinetobacter baumannii has emerged as a clinically significant pathogen that resists to most available antibiotics. Nowadays, colistin (polymyxin E), is one of the last therapeutic options for Acinetobacter baumannii strains. Colistin was recently reintroduced as the last resort for treatment of MDR A. baumannii infections and unfortunately, isolates with colistin resistant A. baumannii has emerged and reportedly increasingly, therefore, alternative antibacterial agents such as phages are urgently required for treatments of MDR Acinetobacter baumannii. Materials and Methods : The clinical bacteria isolated were confirmed by phenotypic and PCR method with bla oxa gene, then out of them MDR isolates by disk diffusion method, were chosen for further investigation. The MIC method was performed for colistin according to CLSI 2018. Biofilm formation was measured by microtiter plate. Phage isolation from the environment was performed. Finally, the effect of phage was tested by MTT assay on the biofilm formation of A. baumannii by co-incubation. Results: Fifteen MDR isolates detected, the MICs of colistin for the resistant isolates ranged from 8 to ≥64 μg/ml. Also, in the biofilm formation assay the most isolates had strong biofilm formation ability. Of those isolates one isolate with strongest biofilm and the most resistance, was chosen for MTT assay. The effectiveness of phage in MoI 10, 1, 0.1, 0.01, 0.001 was found as well. Our study demonstrates that the phage in MoI 0.01 has the best effect on the biofilm formation of the bacteria. Conclusion: With the emergence of antibiotic-resistant bacteria, there is a need to explore the potential therapeutic applications of bacteriophages. The efficacy of phage therapy in our study was evaluated by MTT assay and this experiment demonstrates that phage in MoI 0.01 could be effective on the eradication of biofilm formation in colistin-resistance Acinetobacter baumannii. Efficient bacteriolytic activity and significant reduction of the bacterial biofilm suggests its therapeutic potential to be used for the treatment of infections caused by A. baumannii.