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.