Resistance to cephalosporins and carbapenems in Gram-negative bacterial pathogens.
During the past 15 years, emergence and dissemination of beta-lactam resistance in nosocomial Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii, became a serious problem worldwide. Especially the increasing resistance to 3rd and 4th generation cephalosporins and carbapenems is of particular concern. Gram-negative bacteria pursue various molecular strategies for development of resistance to these antibiotics: (a) generation of extended-spectrum beta-lactamases (ESBL) according to the original definition due to extension of the spectrum of already widely disseminated plasmid-encoded beta-lactamases by amino acid substitution; (b) acquisition of genes encoding ESBL from environmental bacteria as, for instance the CTX-M-type beta-lactamases from Kluyvera spp.; (c) high-level expression of chromosome-encoded beta-lactamase (bla) genes as bla(OXA) or bla(ampC) genes due to modifications in regulatory genes, mutations of the beta-lactamase promoter sequence as well as integration of insertion sequences containing an efficient promoter for intrinsic bla genes; (d) mobilization of bla genes by incorporation in integrons and horizontal transfer into other Gram-negative species such as the transfer of the ampC gene from Citrobacter freundii to Klebsiella spp.; (e) dissemination of plasmid-mediated carbapenemases as KPC and metallo-beta-lactamases, e.g. VIM and IMP; (f) non-expression of porin genes and/or efflux pump-based antibiotic resistance. This mini-review summarizes the historical emergence of beta-lactam resistance and beta-lactamases as major resistance mechanism in enteric bacteria, and also highlights recent developments such as multidrug- and carbapenem resistance.
Robert Koch-Institute, Nosocomial Infections, Wernigerode Branch, Burgstr. 37, 38855 Wernigerode, Germany.
Yvonne
Y
Pfeifer
Angela
A
Cullik
Wolfgang
W
Witte
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015780:Carbapenems / Q000494:pharmacology*; D018550:Cephalosporin Resistance; D002511:Cephalosporins / Q000494:pharmacology*; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D015780:Carbapenems; D002511:Cephalosporins; D001618:beta-Lactamases; C063912:carbapenemase