Abstract
From June to September 2011, a total of 305 ertapenem-nonsusceptible Enterobacteriaceae isolates (MICs of ertapenem ≥ 1 μg/ml) were collected from 11 hospitals in different parts of Taiwan. The MICs of 12 antimicrobial agents against these isolates were determined using the broth microdilution method, and genes for carbapenemases were detected using PCR. Genotypes of isolates possessing carbapenemase genes were identified by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. The ertapenem-nonsusceptible Enterobacteriaceae isolates included Klebsiella pneumoniae (n = 219), Escherichia coli (n = 64), Enterobacter cloacae (n = 15), and other species (n = 7). Seven (2.3%) of the ertapenem-nonsusceptible Enterobacteriaceae isolates exhibited colistin MICs of >4 μg/ml, and 24 (7.9%) were not susceptible to tigecycline (MICs > 2 μg/ml). A total of 29 (9.5%) isolates carried genes encoding carbapenemases, namely, K. pneumoniae carbapenemase-2 (KPC-2) in 16 (7.3%) isolates of K. pneumoniae (KPC-2-KP) and IMP-8 in 5 (2.3%) isolates of K. pneumoniae, 5 (33.3%) isolates of E. cloacae, 1 isolate of E. coli, 1 isolate of Klebsiella oxytoca, and one isolate of Citrobacter freundii. The 16 KPC-2-KP isolates were isolated from patients at four different hospitals in northern Taiwan. All 16 of the KPC-2-KP isolates were susceptible to amikacin and colistin and had a similar pulsotype (pulsotype 1) and the same sequence type (sequence type 11). Infections due to KPC-2-KP mainly occurred in severely ill patients in the intensive care unit (n = 14, 88%). Four patients with infections due to KPC-2-KP died within 14 days of hospitalization. The findings are the first to demonstrate intrahospital and interhospital dissemination of KPC-2-KP in northern Taiwan.