Dissemination of transferable CTX‐M‐type extended‐spectrum β‐lactamase‐producing Escherichia coli in Korea

• Published in: Journal of applied microbiology Vol. 98; no. 4; pp. 921 - 927
• Main Authors: Jeong, S.H., Bae, I.K., Kwon, S.B., Lee, J.H., Song, J.S., Jung, H.I., Sung, K.H., Jang, S.J., Lee, S.H.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.04.2005; Blackwell Science
• Subjects: Adult; Anti-Bacterial Agents - pharmacology; Base Sequence; beta-Lactamases - genetics; Biological and medical sciences; Cefotaxime - pharmacology; Cephalosporin Resistance - genetics; Conjugation, Genetic - genetics; CTX‐M; DNA, Bacterial - genetics; enterobacterial repetitive consensus‐PCR; Escherichia coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - isolation & purification; extended‐spectrum β‐lactamase; Fundamental and applied biological sciences. Psychology; Genes, Bacterial - genetics; Humans; Isoelectric Focusing - methods; Korea; Microbial Sensitivity Tests - methods; Microbiology; PCR‐RFLP; Plasmids - genetics; Polymerase Chain Reaction - methods; Polymorphism, Restriction Fragment Length; β‐lactamase; Asia; Korea; extended-spectrum β-lactamase; Enzyme; Applied microbiology; Escherichia coli; β-Lactamase; PCR-RFLP; enterobacterial repetitive consensus-PCR; Spectrum; Polymerase chain reaction; CTX-M; Restriction fragment length polymorphism; Dissemination; Bacteria; Hydrolases; Enterobacteriaceae
• ISSN: 1364-5072; 1365-2672
• DOI: 10.1111/j.1365-2672.2004.02526.x

Aims:  Among 365 Escherichia coli isolated in 2003, 31 cefotaxime‐resistant isolates were obtained from clinical specimens taken from adults hospitalized in Busan, Korea. Six extended‐spectrum β‐lactamase (ESBL)‐producing isolates were investigated further to determine the mechanism of resistance. Methods and Results:  These isolates were analysed by antibiotic susceptibility testing, pI determination, plasmid profiles, transconjugation test, PCR‐restriction fragment length polymorphism (RFLP), enterobacterial repetitive consensus (ERIC)‐PCR and DNA sequencing. All six of these isolates were found to contain the CTX‐M‐type ESBL genes. Five clinical isolates and their transconjugants produced CTX‐M‐3. One clinical isolate (K17391) and its transconjugant (trcK17391) produced CTX‐M‐15. Five clinical isolates also produced another TEM‐1. One clinical isolate (K12776) also contained another TEM‐52. CTX‐M‐3 ESBL gene was responsible for the resistance to piperacillin, cephalothin, cefotaxime, cefepime and aztreonam. CTX‐M‐15 or TEM‐52 was especially responsible for the resistance to ceftazidime. Conclusions:  These results appear to represent the in vivo evolution of CTX‐M‐type β‐lactamase genes (blaCTX‐M‐3 → blaCTX‐M‐15) under the selective pressure of antimicrobial therapy (especially ceftazidime). PCR‐RFLP is a reliable method to discriminate CTX‐M‐15 gene from CTX‐M‐3 gene. ERIC‐PCR analysis revealed that dissemination of CTX‐M‐3 was not due to a clonal outbreak of a resistant strain but to the intra‐species spread of resistance to piperacillin, cephalothin, cefotaxime, cefepime and aztreonam in Korea. Significance and Impact of the Study:  This is the first report of the occurrence of CTX‐M‐1 cluster ESBLs in Korea. A more comprehensive survey of these ESBL types from Korea is urgently needed because of the in vivo evolution of CTX‐M‐15 from CTX‐M‐3. The emergence of these CTX‐M‐type ESBLs suggests that diagnostic laboratories should screen for ESBLs with ceftazidime as well as cefotaxime; they should still perform clavulanate synergy tests on resistant isolates.