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

Abstract

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 IS Ecp1 or IS CR1 . 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.