Extended-spectrum beta-lactamases.

Resistance to broad-spectrum cephalosporins among Klebsiella pneumoniae has increased significantly, particularly in the intensive care unit setting, in the past decade. The problem has been noted not only in the United States, but around the world. A major mechanism responsible for this is the emergence of extended-spectrum beta-lactamases (ESBLs). These plasmid-mediated beta-lactamases confer resistance to broad-spectrum beta-lactam antibiotics, including third- and fourth-generation cephalosporins, aztreonam, and extended-spectrum penicillins. Other resistances, such as aminoglycoside and trimethoprim-sulfamethoxazole resistance, are often cotransferred on the same plasmid. Fluoroquinolone resistance is also frequently associated, resulting in an organism resistant to most broad-spectrum options. The carbapenems are currently considered the drug of choice for these pathogens. Prevention and control measures are important because of the multiresistant nature of these pathogens. Such traditional infection control measures as contact precautions are recommended. In addition, because this type of antimicrobial resistance appears to be particularly influenced by antibiotic use, antibiotic control measures may also be a very important intervention in controlling the spread of ESBLs.