In Medellin, Colombia, three Pseudomonas aeruginosa isolates with high-level carbapenem resistance (MIC ≥ 256 μg/ml) and an isolate of Citrobacter freundii with reduced susceptibility to imipenem produced the plasmid-mediated class A carbapenemase KPC-2. This is the first report of a KPC-type β-lactamase identified outside of the family Enterobacteriaceae.

In South American countries, the class A extended-spectrum beta-lactamases (ESBLs) so far recognised belong to the CTX-M, Pseudomonas Extended Resistance (PER), SHV and TEM families. ESBL rates in South America are among the highest in the world, probably due to multiple factors. SHV- and TEM-type ESBLs have been frequently encountered, but CTX-M is endemic and widely dominant. PER-type ESBLs seem to be restricted to the southern 'cone' of South America. Community-acquired ESBLs are starting to appear.

During 2005, 66 carbapenem-resistant isolates of Acinetobacter baumannii were collected from seven tertiarycare hospitals participating in a nationwide surveillance network in Colombia. The isolates were multidrug resistant and produced the carbapenemases OXA-23 and OXA-51. Forty-five belonged to four clones while 21 were unique pulsotypes. One clone was present in two hospitals within one city, while another had spread between two hospitals in different cities. Blood, secretions, and abdominal fluids were the most frequent sites of isolation. This is the first description of widespread dissemination of OXA-23 in South America.Acinetobacter baumannii is an important nosocomial pathogen which appears to be increasing in frequency (8). Carbapenems have been the drugs of choice for treatment of severe Acinetobacter infections, but their efficacy is increasingly compromised by resistance (19).According to the SENTRY reports, resistance rates for nosocomial gram-negative pathogens, including A. baumannii, are higher in Latin American countries than in the United States or Europe. The prevalence of carbapenem resistance in A. baumannii isolates across Latin America in the SENTRY database in 2001 was estimated at 25% (13,24). During 2005, carbapenem resistance rates for A. baumannii were around 40% in 12 Colombian tertiary-care hospitals (18).Carbapenem-hydrolyzing OXA enzymes are the most important cause of carbapenem resistance in A. baumannii worldwide (23). These began to be described over a decade ago, in 1993, with the description of ARI-1, later renamed OXA-23, in an imipenem-resistant A. baumannii strain from a patient in the Edinburgh Royal Infirmary (22). The strain was isolated in 1985, before the use of imipenem in the hospital. Imipenem resistance was subsequently demonstrated to be transferable (25). Since then, carbapenem-resistant isolates of A. baumannii carrying oxacillinases have been reported worldwide (4,14,29). It has been recognized that most A. baumannii strains have a chromosomal carbapenemase gene (a bla OXA-51 -like gene) (10), though this is expressed at a high level only if an insertion sequence, such as ISAba1, is inserted upstream (30). In addition, a minority of A. baumannii strains have further OXA carbapenemase genes that are not part of the normal genomic repertoire of the species; these include the bla OXA-23 -like gene, the bla OXA-24 -like gene, and bla . Although they are lessefficient hydrolyzers of carbapenems in vitro than are the metallo-␤-lactamases (M␤Ls), these oxacillinases can inactivate carbapenems and their presence or activation by ISAba1 is demonstrably correlated with resistance (4, 30).Based on the high rates of resistance to carbapenems in A. baumannii strains from 10 tertiary-care hospitals in the Colombian network, an investigation into the underlying mechanisms and strain structure was undertaken.(This report was presented in part at the 46th Annual Interscience Conference on Antimicrobial Agents and Chemotherapy, San Francisco, CA, 2006 [13a].) MATERIALS AND M...

Antibiotic resistance among Gram-negative pathogens in hospitals is a growing threat to patients and is driving the increased use of carbapenems. Carbapenems are potent members of the beta-lactam family of antibiotics, with a history of safety and efficacy for serious infections that exceeds 20 years. Original and review articles were identified from a Medline search (1979-2008). Reference citations from identified publications, abstracts from the Interscience Conferences on Antimicrobial Agents and Chemotherapy and package inserts were also used. Carbapenems are effective in treating severe infections at diverse sites, with relatively low resistance rates and a favourable safety profile. Carbapenems are the beta-lactams of choice for the treatment of infections caused by multidrug-resistant organisms. Optimized dosing of carbapenems should limit the emergence of resistance and prolong the utility of these agents. The newly approved doripenem should prove to be a valuable addition to the currently available carbapenems: imipenem, meropenem and ertapenem.