title: Multidrug resistant Acinetobacter baumannii: risk factors for appearance of imipenem resistant strains on patients formerly with susceptible strains.
abstract: BACKGROUND
  Multidrug resistant Acinetobacter baumannii (MDRAB) is an important nosocomial pathogen usually susceptible to carbapenems; however, growing number of imipenem resistant MDRAB (IR-MDRAB) poses further clinical challenge. The study was designed to identify the risk factors for appearance of IR-MDRAB on patients formerly with imipenem susceptible MDRAB (IS-MDRAB) and the impact on clinical outcomes.
  
  
  RESULTS
  A retrospective case control study was carried out for 209 consecutive episodes of IS-MDRAB infection or colonization from August 2001 to March 2005. Forty-nine (23.4%) episodes with succeeding clinical isolates of IR-MDRAB were defined as the cases and 160 (76.6%) with all subsequent clinical isolates of IS-MDRAB were defined as the controls. Quantified antimicrobial selective pressure, "time at risk", severity of illness, comorbidity, and demographic data were incorporated for multivariate analysis, which revealed imipenem or meropenem as the only significant independent risk factor for the appearance of IR-MDRAB (adjusted OR, 1.18; 95% CI, 1.09 to 1.27). With selected cases and controls matched to exclude exogenous source of IR-MDRAB, multivariate analysis still identified carbapenem as the only independent risk factor (adjusted OR, 1.48; 95% CI, 1.14 to 1.92). Case patients had a higher crude mortality rate compared to control patients (57.1% vs. 31.3%, p = 0.001), and the mortality of case patients was associated with shorter duration of "time at risk", i.e., faster appearance of IR-MDRAB (adjusted OR, 0.9; 95% CI, 0.83 to 0.98).
  
  
  CONCLUSIONS
  Judicious use of carbapenem with deployment of antibiotics stewardship measures is critical for reducing IR-MDRAB and the associated unfavorable outcome.
authors.affiliation: Division of Infectious Diseases, Department of Internal Medicine, Chang Gung Memorial Hospital, Taipei, Taoyuan, Taiwan.
authors.forename: Jung-Jr
authors.initials: JJ
authors.lastname: Ye
authors.forename: Ching-Tai
authors.initials: CT
authors.lastname: Huang
authors.forename: Shian-Sen
authors.initials: SS
authors.lastname: Shie
authors.forename: Po-Yen
authors.initials: PY
authors.lastname: Huang
authors.forename: Lin-Hui
authors.initials: LH
authors.lastname: Su
authors.forename: Cheng-Hsun
authors.initials: CH
authors.lastname: Chiu
authors.forename: Hsieh-Shong
authors.initials: HS
authors.lastname: Leu
authors.forename: Ping-Cherng
authors.initials: PC
authors.lastname: Chiang
mesh_terms: D000151:Acinetobacter Infections / Q000188:drug therapy / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000302:isolation & purification / Q000502:physiology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents; D015780:Carbapenems / Q000494:pharmacology / Q000627:therapeutic use; D016022:Case-Control Studies; D024901:Drug Resistance, Multiple, Bacterial; D006801:Humans; D015378:Imipenem / Q000494:pharmacology* / Q000627:therapeutic use; D008875:Middle Aged; D015999:Multivariate Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D015378:Imipenem