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Objectives:To characterize MDR Escherichia coli from bloodstream infections (BSIs) in Australia, New Zealand and Singapore. Methods:We collected third-generation cephalosporin-resistant (3GC-R) E. coli from blood cultures in patients enrolled in a randomized controlled trial from February 2014 to August 2015. WGS was used to characterize antibiotic resistance genes, MLST, plasmids and phylogenetic relationships. Antibiotic susceptibility was determined using disc diffusion and Etest. Results:A total of 70 3GC-R E. coli were included, of which the majority were ST131 (61.4%). BSI was most frequently from a urinary source (69.6%), community associated (62.9%) and in older patients (median age 71 years). The median Pitt score was 1 and ICU admission was infrequent (3.1%). ST131 possessed more acquired resistance genes than non-ST131 (P = 0.003). Clade C1/C2 ST131 predominated (30.2% and 53.5% of ST131, respectively) and these were all ciprofloxacin resistant. All clade A ST131 (n = 6) were community associated. The predominant ESBL types were blaCTX-M (80.0%) and were strongly associated with ST131 (95% carried blaCTX-M), with the majority blaCTX-M-15. Clade C1 was associated with blaCTX-M-14 and blaCTX-M-27, whereas blaCTX-M-15 predominated in clade C2. Plasmid-mediated AmpC genes (mainly blaCMY-2) were frequent (17.1%) but were more common in non-ST131 (P < 0.001) isolates from Singapore and Brisbane. Two strains carried both blaCMY-2 and blaCTX-M. The majority of plasmid replicon types were IncF. Conclusions:In a prospective collection of 3GC-R E. coli causing BSI, community-associated Clade C1/C2 ST131 predominate in association with blaCTX-M ESBLs, although a significant proportion of non-ST131 strains carried blaCMY-2.

Original publication

DOI

10.1093/jac/dkx466

Type

Journal

The Journal of antimicrobial chemotherapy

Publication Date

03/2018

Volume

73

Pages

634 - 642

Addresses

University of Queensland, UQ Centre for Clinical Research, Royal Brisbane & Women's Hospital, Queensland, Australia.

Keywords

MERINO Trial investigators, Humans, Escherichia coli, Bacteremia, Escherichia coli Infections, Cephalosporins, beta-Lactamases, Bacterial Typing Techniques, Prevalence, Prospective Studies, Phylogeny, Drug Resistance, Bacterial, Genome, Bacterial, Aged, Aged, 80 and over, Middle Aged, Singapore, Australia, New Zealand, Female, Male, Randomized Controlled Trials as Topic, Multilocus Sequence Typing, Whole Genome Sequencing