Genotypic characterization of gentamicin and cephalosporin resistant Escherichia coli isolates from blood cultures in a Norwegian university hospital 2011–2015

Abstract

BackgroundCephalosporin resistance in clinical E. coli isolates is increasing internationally. The increase has been caused by virulent and often multidrug-resistant clones, especially the extended spectrum β-lactamase (ESBL) producing E. coli clone O25b-ST131.MethodsIn Norway, recommended empirical treatment of sepsis consists of gentamicin and penicillin combined, or a broad-spectrum cephalosporin. To investigate if increased gentamicin and cephalosporins resistance rates in our hospital could be caused by specific clones, we conducted a retrospective study on E. coli blood culture isolates from 2011 through 2015. All E. coli isolates non-susceptible to gentamicin and/or third-generation cephalosporins were genotyped using multiple-locus variable-number of tandem repeat analysis (MLVA) and compared with antibiotic susceptible isolates. The frequency of the most common genes causing ESBL production (bla CTX-M, bla ampC) was examined by Real-Time PCR.ResultsA total of 158 cephalosporin and/or gentamicin resistant and 97 control isolates were differentiated into 126 unique MLVA types. Of these, 31% of the isolates belonged to a major MLVA cluster consisting of 41% of the gentamicin resistant and 35% of the cephalosporin resistant isolates. The majority (65/80 isolates) of this MLVA cluster contained MLVA types associated with the E. coli O25b-ST131 clone. Genes encoding CTX-M enzyme phylogroups 1 and 9 occurred in 65% and 19% of cephalosporin resistant isolates, respectively, whereas bla ampC-CIT was identified in 3%.ConclusionNo local E. coli bacteraemia clone was identified. Antibiotic resistance was dispersed over a variety of genotypes. However, association with the international E. coli O25b-ST131 clone was frequent and may be an important driver behind increased resistance rates. Monitoring and preventing dissemination of these resistant clones are important for continued optimal treatment.Electronic supplementary materialThe online version of this article (10.1186/s13756-017-0280-2) contains supplementary material, which is available to authorized users.

Expansion of a Subset Within the C2 Subclade of Escherichia coli Sequence Type 131 (ST131) Is Driving the Increasing Rates of Aminoglycoside Resistance

“…This finding indicates that we need to investigate factors other than antibiotic selection pressure to explain the emergence of C1-M27 as the second most prevalent subclade. In a 4-year study on isolated E. coli strains from blood cultures in Norway, the resistance rate against gentamicin was found to be much higher than that of cephalosporin among O25b-ST131 isolates [ 33 ]. In fact, the appearance of a subpopulation with remarkable resistance to aminoglycosides among ST131, which is notorious for fluoroquinolone resistance and producing ESBL, represents an evolving epidemiology of this clone and its subclades to a pandrug-resistant population [ 34 ].…”