Epidemiological and genomic characteristics of Acinetobacter baumannii from different infection sites using comparative genomics

BackgroundAcinetobacter baumanniiis a common nosocomial pathogen that poses a huge threat to global health. Owing to the severity ofA. baumanniiinfections, it became necessary to investigate the epidemiological characteristics ofA. baumanniiin Chinese hospitals and find the reasons for the high antibiotic resistance rate and mortality. This study aimed to investigate the epidemiologic and genetic characteristics ofA. baumanniiisolated from patients with hospital acquired pneumonia (HAP), bloodstream infection (BSI) and urinary tract infection (UTI) in China and uncover potential mechanisms for multi-drug resistance and virulence characteristics ofA. baumanniiisolates.ResultsAll isolates were classified into two primary clades in core gene-based phylogenetic relationship. Clonal complex 208 (CC208) mainly consisted of ST195 (32 %) and ST208 (24.6 %). CC208 and non-CC208 isolates had carbapenem resistance rates of 96.2 and 9.1 %, respectively. Core genes were enriched in ‘Amino acid transport and metabolism’, ‘Translation’, ‘Energy production and conversion’, ‘Transcription’, ‘Inorganic ion transport and metabolism’ and ‘Cell wall/membrane/envelope synthesis’. Most isolates possessed virulence factors related to polysaccharide biosynthesis, capsular polysaccharide synthesis and motility. Eleven isolates belong to ST369 or ST191 (oxford scheme) all had the virulence factorcap8Eand it had a higher positive rate in UTI (35.3 %) than in BSI (18.9 %) and HAP (12.9 %). ABGRI1 antibiotic resistance islands were responsible for streptomycin, tetracycline and sulfonate resistance. TheblaOXA−23gene was the most probable cause for carbapenem resistance, although theblaOXA−66gene with nonsynonymous SNPs (F82L, I129L) was not.ConclusionsA. baumanniiis a genomically variable pathogen that has the potential to cause a range of infectious diseases. There is high proportion of carbapenem resistance in isolates from all three infection sites (HAP, BSI and UTI), which can be attributed to theblaOXA−23gene. CC208 is the predominant clone inblaOXA−23-carryingA. baumanniithat should be monitored. Virulence factors involving bacteria motility and polysaccharide biosynthesis which are widespread in clinicalA. baumanniistrains deserve our attention.