Extensive Genetic Commonality among Wildlife, Wastewater, Community, and Nosocomial Isolates of Escherichia coli Sequence Type 131 (H30R1 and H30Rx Subclones) That Carry blaCTX-M-27 or blaCTX-M-15
Abstract
Escherichia coli sequence type 131 (ST131) is currently one of the leading causes of multidrug-resistant extraintestinal infections globally. Here, we analyzed the phenotypic and genotypic characteristics of 169 ST131 isolates from various sources (wildlife, wastewater, companion animals, community, and hospitals) to determine whether wildlife and the environment share similar strains with humans, supporting transmission of ST131 between different ecological niches.
Susceptibility to 32 antimicro-bials was tested by disc diffusion and broth microdilution. Antibiotic resistance genes, integrons, plasmid replicons, 52 virulence genes, and fimH-based subtypes were detected by PCR and DNA sequencing.
Genomic relatedness was determined by pulsed-field gel electrophoresis (PFGE). The genetic context and plasmid versus chromosomal location of extended-spectrum beta-lactamase and AmpC beta-lactamase genes was determined by PCR and probe hybridization, respectively.
The 169 ST131 study isolates segregated predominantly into bla(CTX-M-15) H30Rx (60%) and bla(CTX-M-27) H30R1 (25%) subclones. Within each subclone, isolates from different source groups were categorized into distinct PFGE clusters; genotypic characteristics were fairly well conserved within each major PFGE cluster.
Irrespective of source, the bla(CTX-M-15) H30Rx isolates typically exhibited virotype A (89%), an F2:A1:B- replicon (84%), and a 1.7-kb class 1 integron (92%) and had diverse structures upstream of the bla(CTX-M) region. In contrast, the bla(CTX-M-27) H30R1 isolates typically exhibited virotype C (86%), an F1:A2:B20 replicon (76%), and a conserved IS26-Delta ISEcp1-bla(CTX-M)-like structure.
Despite considerable overall genetic diversity, our data demonstrate significant commonality between E. coli ST131 isolates from diverse environments, supporting transmission between different sources, including humans, environment, and wildlife.