Genetic profile of carbapenem-resistant <i>Acinetobacter baumannii</i> strains

Abstract

The purpose of the research: the molecular genetic characteristic ofA. baumanniicarbapenem-resistant strains, including clonal affiliation, resistome and virulome pattern analysis, description of genetic environment resistance determinants, comparative genetic analysis, and assessment of phylogenetic relationships are presented in the work. The studiedA. baumanniistrains belonged to sequence types ST2Pas/ST2062.2063Oxf(n = 5) and ST78Pas/ST1757Oxf(n = 2). The nucleotide sequences of the studiedA. baumanniiST2Pas/ST2062.2063Oxfstrains were grouped into a single cluster according to phylogenetic analysis. And the sequences of theA. baumanniiST78Pas/ST1757Oxfstrains were combined with the nucleotide sequence of theA. baumanniiAbCTX5 strain, isolated in France in 2015. The presence of intrinsic (OXA-51-like) and acquired carbapenemases genes was shown inA. baumanniistrains. In particular,blaOXA-23are identified in members of ST2Pas/ST2062.2063Oxf, and inA. baumanniiST78Pas/ST1757Oxfstrains —blaOXA-72as part of the plasmid DNA. TheA. baumanniiST78Passtrains possessed additional extended-spectrum beta-lactamase genes. Тhe CTX-M-115 cephalosporinase gene are present in both strains, and theA. baumanniistrain NNAb_2023.3 has theblaCARB-16gene. MostA. baumanniistrains are characterized by the presence of acquired genes for enzymatic modification of macrolides(mph(E), msr(E)), chloramphenicols(catB8), aminoglycosides(aadA, aph(3'')-Ib, aph(6)-Id, aac(6')-Ib, aph(3')-Ia, armA). A comparative analysis showed that inA. baumanniiST2Pas/ST2062.2063Oxfstrains the resistance determinants to macrolides and aminoglycosides are located in the Tn6279-like transposon, and the aminoglycosidases genesaph(3'')-Ib, aph(6)-Idare associated with theIS91-like mobile element. InA. baumanniiST78Pas/ST1757Oxfstrains, resistance genes to aminoglycosides, macrolides, sulfonamides, and beta-lactamase genes are grouped in a region from 60 to 80 Kb long between theglmSandhutCgenes. The presence of mutations in thegyrAandparCgenes associated with resistance to fluoroquinolones were characterized in allA. baumanniistrains. Thus, new knowledge about the genetic profile of carbapenem-resistantA. baumanniistrains representing epidemically significant international clonal lineage has been obtained.

Keywords

• a. baumannii
• sequence type
• phylogenetic analysis
• blaoxa-23
• blaoxa-72
• integron
• transposon