title: Influence of genospecies of Acinetobacter baumannii complex on clinical outcomes of patients with acinetobacter bacteremia.
abstract: BACKGROUND
  acinetobacter baumannii complex infections are increasing in prevalence and are associated with a high mortality. Biochemical classification tests cannot differentiate A. baumannii (genospecies 2) from other genospecies. Genospecies typing offers a potential tool to determine whether there are major differences in pathogenicity among the genospecies.
  
  
  METHODS
  adult patients with A. baumannii complex bacteremia in intensive care units were prospectively observed from January 2007 through July 2009. A. baumannii complex was identified by biochemical methods and the Phoenix bacterial identification system. Genospecies were identified by 16S-23S ribosomal RNA intergenic-spacer sequencing.
  
  
  RESULTS
  among the 135 patients with A. baumannii complex bacteremia, 87 (64.4%) had isolates that belonged to genospecies 2, 36 (26.7%) had isolates that belonged to genospecies 13TU, and 12 (8.9%) had isolates that belonged to genospecies 3. Patients with A. baumannii (genospecies 2) bacteremia were more likely to have pneumonia than were patients with bacteremia due to genospecies 13TU (63.2 % vs 27.8%; P =.001), whereas patients with bacteremia due to genospecies 13TU were more likely to have primary bacteremia (69.4% vs 20.7%; P <.001). Genospecies 2 was less susceptible to antibiotics than were other genospecies. It was associated with a higher rate of mortality than was genospecies 13TU (58.6% vs 16.7%; P < .001). On multivariate analysis, genospecies 2 was an independent predictor of mortality (odds ratio, 5.46; 95% confidence interval, 2.00-14.91; P = .001).
  
  
  CONCLUSIONS
  genospecies 2 of the A. baumannii complex was associated with greater resistance to antibiotics and higher mortality among bacteremic patients, compared with other genospecies, especially genospecies 13TU. These findings emphasize the need to focus on genospecies to better understand the pathogenesis and epidemiology of infections caused by the A. baumannii complex.
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Yu-Chung
authors.initials: YC
authors.lastname: Chuang
authors.forename: Wang-Huei
authors.initials: WH
authors.lastname: Sheng
authors.forename: Shu-Ying
authors.initials: SY
authors.lastname: Li
authors.forename: Yu-Chi
authors.initials: YC
authors.lastname: Lin
authors.forename: Jann-Tay
authors.initials: JT
authors.lastname: Wang
authors.forename: Yee-Chun
authors.initials: YC
authors.lastname: Chen
authors.forename: Shan-Chwen
authors.initials: SC
authors.lastname: Chang
mesh_terms: D000151:Acinetobacter Infections / Q000382:microbiology* / Q000401:mortality / Q000473:pathology; D040981:Acinetobacter baumannii / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity*; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016470:Bacteremia / Q000382:microbiology* / Q000401:mortality / Q000473:pathology; D015373:Bacterial Typing Techniques; D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005838:Genotype; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D058889:Molecular Typing; D010802:Phylogeny; D011446:Prospective Studies; D017422:Sequence Analysis, DNA; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer