Carbapenem resistance in Acinetobacter baumannii: mechanisms and epidemiology

Clin Microbiol Infect. 2006 Sep;12(9):826-36. doi: 10.1111/j.1469-0691.2006.01456.x.


The increasing trend of carbapenem resistance in Acinetobacter baumannii worldwide is a concern since it limits drastically the range of therapeutic alternatives. Metallo-beta-lactamases (VIM, IMP, SIM) have been reported worldwide, especially in Asia and western Europe, and confer resistance to all beta-lactams except aztreonam. The most widespread beta-lactamases with carbapenemase activity in A. baumannii are carbapenem-hydrolysing class D beta-lactamases (CHDLs) that are mostly specific for this species. These enzymes belong to three unrelated groups of clavulanic acid-resistant beta-lactamases, represented by OXA-23, OXA-24 and OXA-58, that can be either plasmid- or chromosomally-encoded. A. baumannii also possesses an intrinsic carbapenem-hydrolysing oxacillinase, the expression of which may vary, that may play a role in carbapenem resistance. In addition to beta-lactamases, carbapenem resistance in A. baumannii may also result from porin or penicillin-binding protein modifications. Several porins, including the 33-kDa CarO protein, that constitute a pore channel for influx of carbapenems, might be involved in carbapenem resistance.

Publication types

  • Review

MeSH terms

  • Acinetobacter Infections / drug therapy
  • Acinetobacter Infections / epidemiology*
  • Acinetobacter Infections / microbiology
  • Acinetobacter baumannii / drug effects*
  • Acinetobacter baumannii / enzymology
  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Carbapenems / pharmacology*
  • Humans
  • Microbial Sensitivity Tests
  • beta-Lactam Resistance*
  • beta-Lactamases / genetics
  • beta-Lactamases / metabolism


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • Carbapenems
  • beta-Lactamases
  • carbapenemase
  • oxacillinase