Spread of bla CTX-M-14 Is Driven Mainly by IncK Plasmids Disseminated among Escherichia coli Phylogroups A, B1, and D in Spain

Abstract

ABSTRACT Since its first description in 2000, CTX-M-14 has become one of the most widespread extended-spectrum β-lactamases in Spain. In the present Escherichia coli multilevel population genetic study involving the characterization of phylogroups, clones, plasmids, and genetic platforms, 61 isolates from 16 hospitalized patients and 40 outpatients and healthy volunteers recovered from 2000 to 2005 were analyzed. Clonal relatedness (XbaI pulsed-field gel electrophoresis [PFGE] type, phylogenetic group, multilocus sequence type [MLST]) was established by standard methods. Analysis of transferred plasmids (I- Ceu I; S1 nuclease; restriction fragment length polymorphism analysis; and analysis of RNA interference, replicase, and relaxase) was performed by PCR, sequencing, and hybridization. The genetic environment of bla CTX-M-14 was characterized by PCR on the basis of known associated structures (IS Ecp1 , IS 903 , IS CR1 ). The isolates were mainly recovered from patients in the community (73.8%; 45/61) with urinary tract infections (62.2%; 28/45). They were clonally unrelated by PFGE and corresponded to phylogenetic groups A (36.1%), D (34.4%), and B1 (29.5%). MLST revealed a high degree of sequence type (ST) diversity among phylogroup D isolates and the overrepresentation of the ST10 complex among phylogroup A isolates and ST359/ST155 among phylogroup B1 isolates. Two variants of bla CTX-M -14 previously designated bla CTX-M-14a ( n = 59/61) and bla CTX-M-14b ( n = 2/61) were detected. bla CTX-M-14a was associated with either IS Ecp1 within IncK plasmids ( n = 27), IS CR1 linked to an IncHI2 plasmid ( n = 1), or IS CR1 linked to IncI-like plasmids ( n = 3). The bla CTX-M-14b identified was associated with an IS CR1 element located in an IncHI2 plasmid ( n = 1) or with IS Ecp1 located in IncK ( n = 1). The CTX-M-14-producing E. coli isolates in our geographic area are frequent causes of community-acquired urinary tract infections. The increase in the incidence of such isolates is mostly due to the dissemination of IncK plasmids among E. coli isolates of phylogroups A, B1, and D.