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Volume 42, Number 6, December 2009

Clonal spread of Klebsiella pneumoniae producing CMY-2 AmpC-type β-lactamase in surgical intensive care units

Nan-Yao Lee, Po-Ling Chen, Ching-Chi Lee, Wen-Chien Ko

Received: July 11, 2008    Revised: October 27, 2008    Accepted: November 26, 2008   


Corresponding author:

Dr. Wen-Chien Ko, Division of Infectious Diseases, Department of Internal Medicine, National Cheng Kung University Hospital, No. 138 Shen-Li Rd, Tainan 704, Taiwan. E-mail:


Background and purpose: 

CMY-2, an AmpC-type β-lactamase, has become more prevalent in Klebsiella pneumoniae isolates at the National Cheng Kung University Hospital, Tainan, Taiwan. This retrospective study investigated the epidemiological characteristics of CMY-2–producing strains of K. pneumoniae.


Molecular experiments were performed to describe the blaCMY-2 gene carriage rate and the trend of 
K. pneumoniae isolates with resistance to cefoxitin between January 2001 and June 2003. The epidemiological correlation between patients with blaCMY-2–positive K. pneumoniae was further analyzed and compared by chart review and pulsed-field gel electrophoresis (PFGE).



Of 285 cefoxitin-resistant K. pneumoniae isolates, 69 (24.2%) carried a blaCMY-2 sequence. The first blaCMY-2–positive isolate of each patient was genotyped by PFGE; 49 (89.1%) of 55 were genetically related. Forty five isolates (91.8%) were noted between January and September 2002. Eighteen isolates were from patients in 2 surgical intensive care units (SICUs), and 23 were from patients with prior SICU stays. Compared with patients with non-epidemic CMY-2–producing isolates, patients with the epidemic clone had a shorter duration of hospital stay (p = 0.007) and SICU stay (p = 0.01) before isolation. Recent surgery was independently associated with acquisition of epidemic CMY-2–producing K. pneumoniae.



An unrecognized clonal spread of K. pneumoniae producing CMY-2 AmpC-type β-lactamase in SICUs was found. Cross-transmission of the epidemic clone, suggested by a shorter hospital stay before isolation of the bacterium and the association with recent surgery, highlights the importance of surveillance to recognize an epidemic and initiate control measures.


Key words:

AmpC beta-lactamases; Cross infection; Disease outbreaks; Intensive care units; Klebsiella pneumoniae