Role of megaplasmids and chromosomal integration in acquisition of CTX-M-encoding genes by Pseudomonas aeruginosa.

Abstract

The genes that encode CTX-M-type ESBLs have diffused extensively among Enterobacterales over the past decades.1 Despite this epidemic success at the global level, few of these have been detected (blaCTX-M-1,-2,-3,-14,-15and-43) in the distantly related opportunistic pathogen Pseudomonas aeruginosa.1–4 The narrow host range of plasmids carrying the blaCTX-M determinants in Enterobacterales (mainly of incompatibility group IncF) plausibly accounts for the low prevalence of these resistance genes in P. aeruginosa.5 On the other hand, little is known about the mobile elements that enable the acquisition of CTX-M enzymes by clinical P. aeruginosa strains. One plasmid close to broad-host-range incompatibility group IncP2 has been found to carry the gene blaCTX-M-2, while another one belonging to IncQ harboured blaCTX-M-3.6,7 The present report describes the structure of a large conjugative plasmid determining a novel CTX-M variant, named CTX-M-206, and the genetic environment of a chromosomally located blaCTX-M-15 gene in a P. aeruginosa isolate present in a second strain.