blaCTX-M genes in escherichia coli strains from Croatian Hospitals are located in new (blaCTX-M-3a) and widely spread (blaCTX-M-3a and blaCTX-M-15) genetic structures

Abstract

CTX-M-producing Escherichia coli isolates from three Croatian hospitals were analyzed. All bla(CTX-M-15) genes and one bla(CTX-M-3a) gene resided in widely spread ISEcp1 transposition modules, but other bla(CTX-M-3a) genes were in a new configuration with two IS26 copies, indicating a new event of gene mobilization from a Kluyvera ascorbata genome. The study confirmed the role of the E. coli ST131 clonal group with IncFII-type plasmids in the spread of bla(CTX-M-15) and of IncL/M pCTX-M3-type plasmids in the dissemination of bla(CTX-M-3a).

FIG. 1.

Schematic representation of the genetic structures identified in the study: the ISEcp1-bla_CTX-M-15 (top) and ISEcp1-bla_CTX-M-3a (middle) transposition modules and the IS26-bla_CTX-M-3a-IS26 element (bottom). The structures of the ISEcp1 modules are based on the sequence data from references and . The scheme of the IS26-associated locus is based on sequences of the plasmidic PstI fragments (4,553 bp) cloned in this work. The double horizontal bar indicates a fragment homologous to K. ascorbata DNA (31), while the single thick bar indicates a fragment homologous to the A. baumannii AYE sequence (15). The broken line used to draw the arrow of the transposase pseudo-ORF symbolizes its disruption by the nonframe deletion. Striped boxes refer to the IRL and IRR segments of IS26 and ISEcp1 elements, respectively, including the alternative ISEcp1 IRR located within K. ascorbata orf477 (in the IS26-associated structure shown only for the comparison of Δorf477 fragments in the modules). Black triangles refer to ATG codons of bla_CTX-M and IS26 tnpA genes. PCR primers shown in the diagrams are those that were used for PCR mapping of the bla_CTX-M-carrying modules.