Molecular genetic characterization of multidrug-resistant Acinetobacter baumannii strains and assessment of their sensitivity to phage AP22

Molecular genetic analysis of 130 multidrug-resistant nosocomial Acinetobacter baumannii strains was performed. The strains were obtained from patients admitted to different hospitals in large Russian cities (Chelyabinsk, Moscow, Nizhny Novgorod, and St. Petersburg) in 2005–2010. Species identification was performed by the amplified 16S rRNA gene restriction analysis and by determining the bla _OXA-51-like genes intrinsic for A. baumannii using PCR. Genetic typing of the strains was performed by RAPD-PCR. All strains fell into two clusters, A and B, with the dominant RAPD groups A1 and B1, respectively, including 82% (107 out of 130) of all strains under study. Susceptibility of the strains to bacteriophage AP22 was determined. The phage was shown to infect specifically and to lyse 69% of 130 strains and 82% (88 out of 107) of A. baumannii strains from the dominant RAPD groups. The ability of bacteriophage AP22 to lyse a broad range of clinically relevant A. baumannii strains makes it an attractive candidate for designing phage cocktails intended to control the A. baumannii-associated nosocomial infections. Moreover, the phage can be used for identifying A. baumannii in the bacteriological tests of clinical samples.