Acinetobacter baumannii 2002-2008: increase of carbapenem-associated multiclass resistance in the United States

Microb Drug Resist. 2010 Sep;16(3):209-15. doi: 10.1089/mdr.2010.0052.


The study consisted of data for 55,330 U.S. Acinetobacter baumannii isolates from The Surveillance Network(®) database for the period 2002-2008. Risk factors were time, age, sex, census region, location (Ward or ICU), and isolate source. Antimicrobial susceptibility data were available for carbapenems, cephalosporins, aminoglycosides, fluoroquinolones, and β-lactam/β-lactamase inhibitor combinations. Multiclass resistance was defined as nonsusceptibility to carbapenems and two or more additional classes. Odds of resistance were obtained using a logistic regression model with cubic splines. Carbapenem-associated multiclass resistance has had a 3.7-fold (95% confidence interval [CI] 3.4-4.3) increase from 20.6% in 2002 to 49.2% in 2008. Among blood isolates the increase was by 2.2 times (95% CI 1.7-2.9). Subjects <18 years old had significantly (p < 0.001) lower rates in 2002 (6.9%) than those 65 years or older (21.5%), but by 2008 this difference diminished as rates increased to 44.2% and 54.2%, respectively. A similar divergence was also observed between ICU and Ward, with no differences in 2002, whereas in 2008 ICU isolates had significantly higher rates (55.2%, 95% CI 53.6%-56.9%) than Ward isolates (45.6%, 95% CI 44.2%-47.0%). Over half of all A. baumannii-resistant isolates were carbapenem and multiclass resistant in 2008. Rates among subjects <18 years old have increased faster than those of the elderly, and in the ICU as compared to Ward.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acinetobacter Infections / epidemiology*
  • Acinetobacter Infections / microbiology
  • Acinetobacter baumannii / drug effects*
  • Anti-Bacterial Agents / pharmacology*
  • Carbapenems / pharmacology*
  • Databases, Factual
  • Drug Resistance, Multiple, Bacterial*
  • Hospitalization / statistics & numerical data
  • Humans
  • Internet
  • Logistic Models
  • Microbial Sensitivity Tests
  • Population Surveillance / methods
  • Prevalence
  • Risk Factors
  • United States / epidemiology


  • Anti-Bacterial Agents
  • Carbapenems