Class 1 and 2 Integrons in Hospital Strains of Gram-Negative Bacteria Isolated in Moscow and in Regions of the Russian Federation

Natural systems of cloning and expression of mobile gene cassettes caught by site-specific recombination, class 1 and 2 integrons, play an important role in mobilization and spread of genetic determinants of antibiotic resistance in gram-negative bacterial human pathogens, especially in a hospital environment. The gene cassettes localized in variable parts of integrons determine resistance to antibacterial drugs (AD) of different functional classes. The aim of the work is the detection and characteristic of class 1 and 2 integrons in gram-negative bacteria isolated in multidisciplinary hospitals of Moscow and other regions of the Russian Federation in 2003–2015. Clinical strains of gram-negative bacteria (n = 1248) mainly had multidrug resistance phenotype (94%). An amount of 10% of strains were resistant to AD of three functional groups; 19%, four; 42%, five; 17%, six; and 7%, seven. A high level of resistance of the studied strains to beta-lactams is associated with the presence of beta-lactamase genes of bla_TEM (35% strains), bla_SHV (25%), bla_CTX-M (38%), bla_OXA (31%), bla_VIM (3%), and bla_NDM (2%) types; to AD of other functional groups, with the presence of class 1 integrons (59%) and class 2 integrons (8%). Most class 1 integrons (54%) and class 2 integrons (88%) contained in its variable part 22 variants of gene cassette arrays in class 1 integrons and 4 variants in class 2 integrons. During the study, 31 types of gene cassettes were identified (including the most widespread, aadB, aacA4, aacC1, aadA1, aadA2, aadA5, blaVIM-2, dfrA1, dfrA7, dfrA12, orfC, orfE, orfY, and sat1) associated with the resistance of strains to aminoglycosides, chloramphenicol, sulfonamides, and beta-lactams, as well as orf cassettes encoding the proteins with unknown functions. New gene cassette arrays were identified: dfrA12s-orfF-aadA2 (In1249) and dfrA1-IS911-sat1-aadA1 (not numbered).