Combined use of the Ab105-2фΔCI lytic mutant phage and different antibiotics in clinical isolates of multiresistant Acinetobacter baumannii

Phage therapy is an abandoned antimicrobial therapy that has been resumed in recent years. In this study, we mutated a lysogenic phage from Acinetobacter baumannii into a lytic phage (Ab105-2phiΔCI) showing antimicrobial activity against A.baumannii clinical strains(such as Ab177_GEIH-2000 which showed MICs to meropenem and imipenem of 32 μg/ml and 16 μg/ml, respectively as well as belonging to GEIH-REIPI Spanish MulticenterA. baumannii Study II 2000/2010, Umbrella Genbank Bioproject PRJNA422585).We observed in vitro, an antimicrobial synergistic effect(from 4 log to 7 log CFU/ml) with meropenem plus lytic phage in all combinations analysed(0.1, 1 and 10 MOI of Ab105-2phiΔCI mutant as well as 1/4 and 1/8 MIC of meropenem). Moreover, we had a decrease in bacterial growth of 8 log CFU/ml for the combination of imipenem at 1/4 MIC plus lytic phage(Ab105-2phiΔCI mutant) and of 4 log CFU/ml for the combination of imipenem at 1/8 MIC plus lytic phage (Ab105-2phiΔCI mutant) in both MOI 1 and 10.These results were confirmed in in vivo(G. mellonella) obtaining a higher effectiveness in thecombination of imipenem and Ab105-2phiΔCI mutant(P<0.05). This approach could help to reducethe emergence of phage resistant bacteria and restore sensitivity to the antibiotics when used tocombat multiresistant strains of Acinetobacter baumannii

Combined Use of the Ab105-2φΔCI Lytic Mutant Phage and Different Antibiotics in Clinical Isolates of Multi-Resistant Acinetobacter baumannii

Phage therapy is an abandoned antimicrobial therapy that has been resumed in recent years. In this study, we mutated a lysogenic phage from Acinetobacter baumannii into a lytic phage (Ab105-2phi∆CI) that displayed antimicrobial activity against A. baumannii clinical strain Ab177_GEIH-2000 (isolated in the GEIH-REIPI Spanish Multicenter A. baumannii Study II 2000/2010, Umbrella Genbank Bioproject PRJNA422585, and for which meropenem and imipenem MICs of respectively, 32 μg/mL, and 16 μg/mL were obtained). We observed an in vitro synergistic antimicrobial effect (reduction of 4 log–7 log CFU/mL) between meropenem and the lytic phage in all combinations analyzed (Ab105-2phi∆CI mutant at 0.1, 1 and 10 MOI and meropenem at 1/4 and 1/8 MIC). Moreover, bacterial growth was reduced by 8 log CFU/mL for the combination of imipenem at 1/4 MIC plus lytic phage (Ab105-2phi∆CI mutant) and by 4 log CFU/mL for the combination of imipenem at 1/8 MIC plus lytic phage (Ab105-2phi∆CI mutant) at both MOI 1 and 10. These results were confirmed in an in vivo model (G. mellonella), and the combination of imipenem and mutant Ab105-2phi∆CI was most effective (p < 0.05). This approach could help to reduce the emergence of phage resistant bacteria and restore sensitivity to antibiotics used to combat multi-resistant strains of Acinetobacter baumannii