Abstract
Clonal lineages of ESBL (Extended-Spectrum β-Lactamase)-producing E. coli belonging to sequence type 131 (ST131) have disseminated globally during the last 30 years, leading to an increased prevalence of resistance to fluoroquinolones and extended-spectrum cephalosporins in clinical isolates of E. coli. We aimed to study if Swedish ESBL-producing ST131 isolates originated from single or multiple introductions to the population by assessing the amount of genetic variation, on chromosomal and plasmid level, between Swedish and international E. coli ST131. Bayesian inference of Swedish E. coli ST131 isolates (n = 29), sequenced using PacBio RSII, together with an international ST131 dataset showed that the Swedish isolates were part of the international ST131 A, C1 and C2 clades. Highly conserved plasmids were identified in three clusters although they were separated by several years, which indicates a strong co-evolution between some ST131 lineages and specific plasmids. In conclusion, the tight clonal relationship observed within the ST131 clades, together with highly conserved plasmids, challenges investigation of strain transmission events. A combination of few SNPs on a genome-wide scale and an epidemiological temporospatial link, are needed to track the spread of the ST131 subclones.
Highlights
Few antibiotic resistant clones have generated as much interest as Escherichia coli sequence type 131 (ST131)
The selected ESBL-producing E. coli ST131 isolates were from patients with bloodstream infection (n = 20) and from non-symptomatic community carriers (n = 9) in Sweden (Supplementary Table S1, deposited in NCBI under BioSample accession SAMN10839615 to 43)
The isolates were selected based on heterogeneity in their phenotypic resistance pattern, blaCTX-M gene type and plasmid replicon type to achieve a broad representation of the ST131 population in Sweden
Summary
Few antibiotic resistant clones have generated as much interest as Escherichia coli ST131. Given the low prevalence of ESBL-producing and low antibiotic selection pressure in Sweden, we hypothesised that ST131 isolates from Swedish carriers and patients would cluster with international clones in several different clades, if observed cases are mainly due to constant influx. This hypothesis was investigated by constructing a phylogeny of ESBL-producing ST131 isolates from i) patients with bloodstream infections and ii) non-symptomatic community carriers in Sweden in relation to previously published international ST131 isolates[3].
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