Klebsiella pneumoniae carbapenemases in Enterobacteriaceae: history, evolution, and microbiology concerns.
Since the discovery of penicillin 80 years ago, gram-negative bacteria have become proficient at evading the lethal activity of β-lactam antibiotics, principally through the production of β-lactamases. The rapid emergence of penicillinases in both gram-positive and gram-negative bacteria led to the development of cephalosporin β-lactam antibiotics, but production of plasmid-mediated extended-spectrum cephalosporinases (or extended-spectrum β-lactamases) and AmpC enzymes resulted in resistance to this drug class. Because carbapenems were the only β-lactam agents active against such extended-spectrum β-lactamase-producing strains, appropriate and inappropriate use soon resulted in Enterobacteriaceae resistance. As a result, two distinct types of carbapenemases-the metallo-β-lactamases and Klebsiella pneumoniae carbapenemases (KPCs)-were soon identified. The KPCs comprise 10 variants that differ from one another by one to three amino acid substitutions (KPC-2 to KPC-11). The KPC-producing Enterobacteriaceae are not only multidrug resistant but are also difficult to detect routinely in the clinical microbiology laboratory. Tigecycline, polymyxins (colistin and polymyxin B), and aminoglycosides are possible candidate therapies for infections caused by KPC-producing organisms, although well-conducted clinical trials are required to fully define their roles in patient management. The shortage of new antimicrobial agents on the immediate horizon suggests that enhanced adherence with infection prevention procedures and antimicrobial stewardship programs are needed to curb patient-to-patient transmission and to reduce the selection of multidrug-resistant bacteria.