Contemporary activity of colistin and polymyxin B against a worldwide collection of Gram-negative pathogens: results from the SENTRY Antimicrobial Surveillance Program (2006-09)

J Antimicrob Chemother. 2011 Sep;66(9):2070-4. doi: 10.1093/jac/dkr239. Epub 2011 Jun 29.


Objectives: To comparatively evaluate the antimicrobial activities of colistin and polymyxin B with those of other antimicrobials against a worldwide collection of 40 625 Gram-negative bacilli.

Methods: Antimicrobial susceptibility testing was performed and interpreted using the CLSI broth microdilution method except for colistin against Enterobacteriaceae.

Results: The polymyxins showed potent in vitro activities (MIC₉₀, ≤ 0.5-1 mg/L) against this large collection of clinical isolates, with very low resistance rates (< 0.1%-1.5%). Resistance to the polymyxins remained stable among organisms tested except for Klebsiella spp. isolates collected from the Asia-Pacific and Latin American regions, where a trend towards greater resistance was observed (P ≤ 0.05). In addition, an important reduction in imipenem susceptibility among Acinetobacter spp. and Klebsiella spp. was demonstrated in most geographical regions.

Conclusions: Although the polymyxins showed excellent in vitro activity against the vast majority of Gram-negative bacilli evaluated, a trend to greater resistance was observed in the Asia-Pacific and Latin American regions. Therefore, the clinical use of polymyxins must be cautious and surveillance monitored.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Brazil / epidemiology
  • Colistin / pharmacology*
  • Drug Resistance, Bacterial
  • Europe / epidemiology
  • Geography
  • Gram-Negative Bacteria / drug effects*
  • Gram-Negative Bacterial Infections / drug therapy*
  • Gram-Negative Bacterial Infections / microbiology*
  • Humans
  • Microbial Sensitivity Tests
  • Polymyxin B / pharmacology*
  • Population Surveillance


  • Anti-Bacterial Agents
  • Polymyxin B
  • Colistin