The CTX-M Conundrum: Dissemination of Plasmids and Escherichia Coli Clones

Microb Drug Resist. 2011 Mar;17(1):83-97. doi: 10.1089/mdr.2010.0132. Epub 2011 Jan 31.


The ongoing global spread and increased prevalence of CTX-M-type extended-spectrum β-lactamases in Enterobacteriaceae is of great concern. The successful distribution of CTX-M enzymes mainly involves Escherichia coli causing systemic as well as urinary tract infections in patients worldwide. CTX-M expression is often associated with coresistance that critically reduces treatments options. The mobilization of bla(CTX-M) genes from their original chromosomal position in various Kluyvera species has been facilitated by mobile genetic elements such as ISEcp1 or ISCR1. Molecular epidemiological studies have revealed a thriving linkage of bla(CTX-M) genes to conjugative plasmids and successful bacterial clones. Multireplicon FII plasmids are shown to carry the most widely distributed bla(CTX-M-15) across continents, paving the way for bla(CTX-M-15) into different genetic lineages of E. coli. Dissemination of virulent clones ST131-O25:H4-B2 and ST405-O102:H6-D is now being described worldwide. Importantly, CTX-M-producing strains are uncovering their ability of long-term gastrointestinal colonization often associated with travel to high-prevalent areas. Thus, we are witnessing a global epidemic of bla(CTX-M)-encoding E. coli strains and plasmids, which require serious attention and efficient infection control measures.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Anti-Bacterial Agents / pharmacology
  • Drug Resistance, Bacterial / genetics
  • Escherichia coli / genetics*
  • Escherichia coli / isolation & purification
  • Escherichia coli Infections / epidemiology
  • Escherichia coli Infections / microbiology*
  • Humans
  • Molecular Epidemiology / methods
  • Plasmids / genetics
  • beta-Lactamases / genetics*


  • Anti-Bacterial Agents
  • beta-Lactamases