title: Effectiveness of tigecycline-based versus colistin- based therapy for treatment of pneumonia caused by multidrug-resistant Acinetobacter baumannii in a critical setting: a matched cohort analysis.
abstract: BACKGROUND
  Colistin and tigecycline have both been shown good in vitro activity among multi-drug resistant Acinetobacter baumannii (MDRAB). A comparative study of colistin versus tigecycline for MDRAB pneumonia is lacking.
  
  
  METHODS
  The study enrolled adults with MDRAB pneumonia admitted to intensive care units at a referral medical center during 2009-2010. Since there were no standardized minimum inhibitory concentration (MIC) interpretation criteria of tigecycline against A. baumannii, MIC of tigecycline was not routinely tested at our hospital. During the study periods, MIC of colistin was not routinely tested also. We consider both colistin and tigecycline as definite treatments of MDRAB pneumonia. Patients who received tigecycline were selected as potential controls for those who had received colistin. We performed a propensity score analysis, by considering the criteria of age, gender, underlying diseases, and disease severity, in order to match and equalize potential prognostic factors and severity in the two groups.
  
  
  RESULTS
  A total of 294 adults with MDRAB pneumonia were enrolled, including 119 who received colistin and 175 who received tigecycline. We matched 84 adults who received colistin with an equal number of controls who received tigecycline. The two well matched cohorts share similar characteristics: the propensity scores are colistin: 0.37 vs. tigecycline: 0.37, (P = .97); baseline creatinine (1.70 vs. 1.81, P = .50), and the APACHE II score (21.6 vs. 22.0, P = .99). The tigecycline group has an excess mortality of 16.7% (60.7% vs. 44%, 95% confidence interval 0.9% - 32.4%, P = .04). The excess mortality of tigecycline is significant only among those with MIC >2 μg/mL (10/12 vs. 37/84, P = .01), but not for those with MIC ≦ 2 μg/mL (4/10 vs. 37/84, P = .81).
  
  
  CONCLUSIONS
  Our data disfavors the use of tigecycline-based treatment in treating MDRAB pneumonia when tigecycline and colistin susceptibilities are unknown, since choosing tigecycline-based treatment might result in higher mortality. The excess mortality of tigecycline-based group may be related to higher MIC of tigecycline (> 2 μg/mL). Choosing tigecycline empirically for treating MDRAB pneumonia in the critical setting should be cautious.
authors.forename: Yu-Chung
authors.initials: YC
authors.lastname: Chuang
authors.forename: Chien-Yu
authors.initials: CY
authors.lastname: Cheng
authors.affiliation: Department of Internal Medicine, National Taiwan University Hospital, No, 7 Chung-Shan South Road, Taipei 100, Taiwan. whsheng@ntu.edu.tw.
authors.forename: Wang-Huei
authors.initials: WH
authors.lastname: Sheng
authors.forename: Hsin-Yun
authors.initials: HY
authors.lastname: Sun
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 / Q000188:drug therapy*; D040981:Acinetobacter baumannii / Q000187:drug effects; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D003091:Colistin / Q000627:therapeutic use*; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D008911:Minocycline / Q000031:analogs & derivatives* / Q000627:therapeutic use; D011014:Pneumonia / Q000188:drug therapy*; D012189:Retrospective Studies; D013624:Taiwan; D000078304:Tigecycline
chemical_list: D000900:Anti-Bacterial Agents; D000078304:Tigecycline; D008911:Minocycline; D003091:Colistin