Carbapenem resistance in Acinetobacter baumannii: mechanisms and epidemiology.
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.
Poirel
L
L
Service de Bactériologie-Virologie, Hôpital de Bicêtre, South-Paris Medical School, University Paris XI, Le Kremlin-Bicêtre, France. laurent.poirel@bct.ap-hop-paris.fr
Nordmann
P
P
D000151:Acinetobacter Infections / Q000188:drug therapy / Q000453:epidemiology* / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000187:drug effects* / Q000201:enzymology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015780:Carbapenems / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D001618:beta-Lactamases; C063912:carbapenemase; C108449:oxacillinase