Detection of Klebsiella pneumoniae Carbapenemase (KPC) Production in Non-Klebsiella pneumoniae Enterobacteriaceae Isolates by Use of the Phoenix, Vitek 2, and Disk Diffusion Methods

In this study, we tested the abilities of the Vitek 2, BD Phoenix, and Kirby Bauer disk diffusion tests to detect carbapenemase production in a collection of 14 Klebsiella pneumoniae carbapenemase (KPC)-producing non-Klebsiella pneumoniae isolates. In addition, we evaluated 13 KPC-positive K. pneumoniae isolates by using each of these methods and applied both 2009 and 2010 CLSI carbapenem interpretive guidelines. Klebsiella pneumoniae carbapenemases (KPC) are Ambler class A plasmid-encoded enzymes that are capable of hydro-lyzing all beta-lactam antibiotics, including monobactams, ex-tended-spectrum cephalosporins, and carbapenems. The KPC enzyme was originally described in 2001 in a Klebsiella pneu-moniae isolate from North Carolina (18). Since then, KPC has disseminated worldwide and, although harbored predomi-nantly by Klebsiella pneumoniae, has also been identified in numerous other genera of the Enterobacteriaceae (1, 8, 15, 17). Many clinical microbiology laboratories utilize automated in vitro susceptibility testing systems, but some of these hav