Microbiological features of KPC-producing Enterobacter isolates identified in a U.S. hospital system

Microbiological data regarding Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacter spp. are scarce. In this study, 11 unique KPC-producing Enterobacter isolates were identified among 44 ertapenem-nonsusceptible Enterobacter isolates collected between 2009 and 2013 at a hospital system in Western Pennsylvania. All cases were healthcare-associated and occurred in medically complex patients. While pulsed-field gel electrophoresis showed diverse restriction patterns overall, multilocus sequence typing identified Enterobacter cloacae isolates with sequence types 93 and 171 from 2 hospitals each. The levels of carbapenem minimum inhibitory concentrations were highly variable. All isolates remained susceptible to colistin and tigecycline, and the majority, to amikacin and doxycycline. A bla_KPC-carrying IncN plasmid conferring trimethoprim-sulfamethoxazole resistance was identified in 3 of the isolates. Spread of bla_KPC in Enterobacter spp. appears to be due to a combination of plasmid-mediated and clonal processes.