CTX-M-type beta-lactamases: an emerging group of extended-spectrum enzymes

CTX-M-type beta-lactamases constitute a novel group of class A beta-lactama ses with extended-spectrum properties. They are encoded by transferable pla smids and found in various enterobacteria, mostly Salmonella typhimurium, E scherichia coli, Klebsiella pneumoniae and Proteus mirabilis. CTX-M enzymes share extensive sequence similarity with the chromosomal beta-lactamases o f Klebsiella oxytoca. They efficiently hydrolyze many newer broad-spectrum oximino-beta-lactams including cefotaxime, ceftriaxone and aztreonam and ar e readily inhibited by tazobactam and clavulanate. CTX-M-producing enteroba cteria are endemic in Latin America and in some areas of North Eastern Euro pe. Data on their structure, properties and epidemiology are discussed. (C) 2000 Published by Elsevier Science B.V. and International Society of Chemo therapy. All rights reserved.