Emergence and dissemination of Enterobacteriaceae isolates harboring 
carbapenemases in various geographic regions represents a significant threat to 
the management of nosocomial infections. Enterobacteriaceae isolates from the 
SENTRY Antimicrobial Surveillance Program (2000-2004) demonstrating decreased 
susceptibility to imipenem and meropenem (minimum inhibitory concentration 
[MIC], > or =2 mg/L) were evaluated for the production of 
metallo-beta-lactamases and serine carbapenemases using disk approximation and 
polymerase chain reaction (PCR) tests. Carbapenemase-producing strains were 
epidemiologically typed by automated riboprinting and pulsed-field gel 
electrophoresis (PFGE) to establish clonality. Among 37,557 Enterobacteriaceae 
(5 genus groups) evaluated, 119 (0.32%) had increased carbapenem MIC values, and 
a carbapenemase was identified in 51 (42.9%) of these strains. KPC-2 and KPC-3 
were the most frequently occurring carbapenemases (24 isolates, 20.2%) in the 
United States and were detected in Klebsiella spp, Citrobacter spp., 
Enterobacter spp., and Serratia marcescens strains isolated in New York, 
Arkansas, and Virginia. SME-2-producing S. marcescens were isolated in the New 
York City area, Texas, and Ohio, while NMC-A was found in one E. cloacae strain 
from New York. In contrast, metallo-beta-lactamases were prevalent in Europe. 
IMP-1-producing E. cloacae (11 isolates) were detected in Turkey, while 
VIM-1-producing strains were found in Italy (Enterobacter spp.) and Greece 
(Klebsiella pneumoniae). Clonal dissemination of carbapenemase-producing strains 
was observed in several medical centers on both continents. The occurrence of 
carbapenemases in various Enterobacteriaceae remains rare but appears to be 
spreading geographically (not in Latin America), mainly with 
metallo-beta-lactamases being found in Mediterranean Europe and KPC enzymes in 
the New York City area.