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KMID : 0829320080110020090
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Korean Journal of Clinical Microbiology
2008 Volume.11 No. 2 p.90 ~ p.97
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Detection of CTX-M-Type Extended-Spectrum β-Lactamase in Clinical Isolates of Chromosomal AmpC β-Lactamase-Producing Enterobacteriaceae from Korea and Their Molecular Characteristics
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Kim Chang-Ki
Lee Kyung-Won
Yong Dong-Eun
Chong Yun-Sop
Yum Jong-Hwa
Jeong Seok-Hoon
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Abstract
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Background: Clinical isolates of AmpC β-lactamase producing Enterobacteriaceae were evaluated to determine the prevalence of CTX-M extended-spectrum β-lactamases (ESBLs) and their genetic environments.
Methods: A total of 250 non-duplicate isolates of Eneterobacter aerogenes, E. cloacae, Citrobacter freundii, Serratia marcescens and Morganella morganii were collected at a Korean hospital. ESBL production was determined by double disk synergy test. For ESBL producers, bla genes were sequenced and
blaCTX-M environment was characterized by PCR mapping and sequencing.
Results: Among the 250 isolates 29 (11.6%) produced ESBL, and 14 of the 29 isolates produced CTX-M ESBLs, including CTX-M-9 by 8 isolates, CTX-M-3 by 4 isolates, CTX-M-12 by 1 isolate, and CTX-M-14 by 1 isolate. ISEcp1 was present upstream of blaCTX-M-3, 12, and 14. Three of the four CTXM-3 producers had the same genetic environment (pemK-ISEcp1-blaCTX-M-3-orf477-mucA). An IS903-like element was found downstream of blaCTX-M-14. ISCR1 was identified upstream of blaCTX-M-9 and ISCR1 and blaCTX-M-9 were located on sul1-type class 1 integron. The variable region between the 5’-CS and the first 3’-CS contained dfrA16 and aadA2. Its structure was similar to that of In60, but our isolates did not have IS3000 or second 3’-CS.
Conclusion: CXT-M type ESBL was prevalent in AmpC β-lactamase-producing Enterobacteriaceae, particularly E. cloacae. blaCTX-M genes were associated with ISEcp1 or ISCR1. This is the first report on the genetic environment of blaCTX-M in Korean isolates. (Korean J Clin Microbiol 2008;11:90-97)
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KEYWORD
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Extended-spectrum β-lactamase, CTX-M, Genetic characteristics
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