DIVERSITY OF ANTIBIOTIC RESISTANCE PLASMIDS IN EPIDEMIC ESCHERICHIA COLI ST131 IN ISRAEL
Background: The worldwide Escherichia coli sequence type ST131 emerged in Israel in 2003 (Karfunkel et al., 2013) and became a highly important multidrug resistant pathogen. We identified ST131 clone in several human (hospital and community) and animal E. coli collections (2003-2016), and chose 22 extended-spectrum-β-lactamase-(ESBL)-encoding plasmids to investigate resistance spread within this clone.
Methods: Plasmids were purified from 22 E. coli ST131 causing human bloodstream infections (BSI-EC, 2003-2016, n=14) and urinary tract infections (UPEC, 2015, n=6), or carried asymptomatically in companion animals (A-EC, 2015, n=2). Sequencing was done using the Illumina HiSeq platform, and scaffolds were assembled using SPAdes v3.10.0. Bioinformatic analyses were performed for plasmid comparison and gene mapping.
Results: All plasmids sized >100Kb, and carried blaCTX-M-ESBL-genes. 19 plasmids were self-conjugable, typed as IncF, and encoded 5-10 antibiotic resistance genes (ARGs) conferring resistance to more than 3 antibiotic classes. Three identical plasmids (from 2 BSI-EC and 1 A-EC) with an unknown replicon type were unconjugable, carried a single ARG, blaCTX-M-15, and were found to be identical with pECOH89, an E. coli plasmid isolated in Germany. 16/22 plasmids were classified into three related groups each carrying a distinct ESBL gene (untypable blaCTX-M-15, IncF[F2:A1:B-] blaCTX-M-15, and IncF[F1:A2:B20] blaCTX-M-27 plasmids). A group of IncF blaCTX-M-15 plasmids originated from BSI, and other groups consisted of plasmids from different sources. We identified the enterotoxin gene, senB, in seven of our plasmids, mostly among the UPEC isolates (n=4), two BSI-EC and one A-EC. senB was common within the blaCTX-M-27-encoding plasmid group.
Conclusions: E. coli ST131 spreads in Israel harboring diverse plasmids that are sufficient for multidrug resistance phenotype, suggesting resistance development via clonal expansion and horizontal gene transfer.
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