The Emerging Strong Among Extended-Spectrum beta-Lactamases: CTX-M Enzymes / 병원감염관리

ABSTRACT

CTX-M-type extended-spectrum beta-lactamases (ESBLs) are the most wide spread enzymes among non-TEM and non-SHV plamid-mediated ESBLs, and have been found predominantly in Escherichia coli. CTX-M ESBLs have a wide substrate range, including penicillins and narrow- and expanded-spectrum cephalosporins, and as the designation "CTX" refers, these enzymes preferentially hydrolyze cefotaxime but not ceftazidime. At present, the CTX-M family comprises more than 60 enzymes that can be subclassified into 5 clusters by amino acid sequence similarities. In Korea, members of CTX-M-1 (CTX-M-3, CTX-M-12, CTX-M-15, and CTX-M-54) and CTX-M-9 (CTX-M-9 and CTX-M-14) clusters have been found. The rapid dissemination of CTX-M ESBLs involves strain or plasmid epidemics, but it also involves mobile elements including ISEcp1-like insertion sequences and ISCR1 element. A recent report shows that the blaCTX-M-14 gene from Korea is associated with not only ISEcp1-like insertion sequences but also ISCR1 element. ISCR1 element is a powerful genetic tool that can mobilize antibiotic resistance genes; therefore, further spread of the blaCTX-M-14 gene can be anticipated.