Korean J Clin Microbiol.  2008 Oct;11(2):90-97. 10.5145/KJCM.2008.11.2.90.

Detection of CTX-M-Type Extended-Spectrum beta-Lactamase in Clinical Isolates of Chromosomal AmpC beta-Lactamase-Producing Enterobacteriaceae from Korea and Their Molecular Characteristics

Affiliations
  • 1Korean Institute of Tuberculosis, The Korean National Tuberculosis Association, Seoul, Korea.
  • 2Department of Biomedical Laboratory Science, Dong-Eui University College of Natural Science, Busan, Korea.
  • 3Department of Laboratory Medicine, Yonsei University College of Medicine, Seoul, Korea. leekcp@yuhs.ac
  • 4Research Institute of Bacterial Resistance, Yonsei University College of Medicine, Seoul, Korea.

Abstract

BACKGROUND: Clinical isolates of AmpC beta-lactamase- producing Enterobacteriaceae were evaluated to determine the prevalence of CTX-M extended-spectrum beta-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 CTX- M-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 beta-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.

Keyword

Extended-spectrum beta-lactamase; CTX- M; Genetic characteristics

MeSH Terms

beta-Lactamases
Citrobacter freundii
Cloaca
Enterobacteriaceae
Integrons
Korea
Morganella morganii
Polymerase Chain Reaction
Prevalence
Serratia marcescens
beta-Lactamases
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