Carbapenemases in enterobacteria, Hong Kong, China, 2009

DOI: 10.3201/eid1701.101443
Suggested citation for this article: Chu Y-W, Tung VWN, Cheung TKM, Chu M-Y, Cheng N, Lai C, et al. Carbapenemases in enterobacteria, Hong Kong, China, 2009 [letter]. Emerg Infect Dis. 2011 Jan; [Epub ahead of print]
Carbapenemases in Enterobacteria, Hong Kong, China, 2009

To the Editor: Carbapenems are often the recommended treatment for serious infections caused by extended-spectrum β-lactamase–producing enterobacteria. However, enzyme-mediated carbapenem resistance is increasingly reported worldwide. Carbapenemases are represented by 3 molecular classes of β-lactamase: A, B, and D (1). The best known class A carbapenemase is Klebsiella pneumoniae carbapenemase (KPC); KPC-producing enterobacteria are responsible for many hospital outbreaks. Class B carbapenemases are metallo-β-lactamases (MBL), which have the widest substrate spectrum. Class D OXA-type carbapenemases are found mainly in nonfermenting bacteria, except for OXA-48, which has been found only in enterobacteria.

In Hong Kong Special Administrative Region, People’s Republic of China, the Public Health Laboratory Centre routinely provides microbiological diagnostic services for government outpatient clinics and confirms the identity of bacterial isolates referred by other clinical laboratories. In 2009, among 18 enterobacteria isolates determined to be not susceptible to carbapenem, only 4 isolates—Citrobacter freundii, Enterobacter cloacae, Escherichia coli, and K. pneumoniae—were confirmed to produce carbapenemase. The E. coli isolate was from a government outpatient clinic; the others were from a regional hospital laboratory (Table).

For all 4 isolates, the modified Hodge test (2) demonstrated enzyme activity against ertapenem and meropenem. Previously described PCR and sequencing methods (1) identified the MBL IMP-4 in the C. freundii and K. pneumoniae isolates; the C. freundii isolate also possessed extended-spectrum β-lactamase CTX-M-9. The E. coli isolate harbored the recently described MBL called New Delhi metallo-β-lactamase (NDM-1) (GenBank accession no. FN396876) from India (3). The E. cloacae isolate possessed a class A carbapenemase IMI-like (Nmc-type) gene,...

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