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Escherichia coli belonging to ST131 rarely transfers blactx-m-15 to fecal Escherichia coli

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Background: Extended spectrum beta-lactamase (ESBL)-producing Escherichia coli (E. coli) causing urinary tract infections often belong to sequence type 131 (ST131), serotype O25, carrying blaCTX-M-15.

Aim: The main aim of this study was to examine the conjugational frequencies of E. coli with plasmids carrying blaCTX-M-15 to E. coli isolates from the fecal flora of healthy humans to determine whether ST131 is more likely to uptake or donate ESBL resistance compared to other E. coli clones.

Methods: Donors and recipients were all clinical isolates and did not harbor plasmids with identical incompatibility groups (Inc-groups) based on in silico analyses of Inc-groups and restriction/modification systems (R/M-systems). The in vitro conjugation experiments were performed as filter conjugation with verification of transconjugants by random amplified polymorphic DNA (RAPD) PCR and blaCTX-M-15 PCR.

Results: The frequencies of conjugation with blaCTX-M-15-carrying plasmids were found to be very rare with detectable conjugation frequencies in the range of 4x10-9-7x10-7 transconjugants/recipient. Recipients of O25/ST131 type yielded significantly lower conjugation frequencies compared to recipients of other O-types (P=0.004). The applied ST131/O25 donors did not yield detectable levels of transconjugants regardless of the applied recipient. Presence of sub-MIC levels of ampicillin increased plasmid transfer frequencies x100 fold (P=0.07).

Conclusion: The results indicate that blaCTX-M-15 is rarely transferred by conjugation to E. coli isolates of the intestinal flora, even when the gene is plasmid-borne.

Original languageEnglish
JournalInfection and Drug Resistance
Pages (from-to)2429-2435
Number of pages7
Publication statusPublished - 2019

ID: 59000220