2009. Mechanisms of Quinolone Resistance in Enterotoxigenic Escherichia coli Isolates from Peruvian Children
Session: Poster Abstract Session: Antimicrobial Resistance Mechanisms
Saturday, October 29, 2016
Room: Poster Hall
  • ETEC quinolone IDWeek 26Oct2016.pdf (317.8 kB)
  • Background: Quinolones and azithromycin remain as drugs of choice for the treatment of Enterotoxigenic Escherichia coli(ETEC) infections, especially for traveler´s diarrhea in Peru. The aim of this study was to determine the mechanisms of quinolone resistance in ETEC strains isolated from Peruvian children.

    Methods: We analyzed a total of 205 ETEC strains previously isolated from two cohort studies in children <24 months of age in Lima, Peru. ETEC was identified by a multiplex real-time PCR for lt and/or stgenes. Susceptibility to nalidixic acid (Nal) and ciprofloxacin (Cip) was tested by disk diffusion. Among ETEC isolates exhibiting resistance or diminished susceptibility to Nal, the presence of target mutations and transferable mechanisms of quinolone resistance (TMQR) were determined by PCR and sequencing. Additionally, the role of Phe-Arg-β-Naphtylamyde inhibitible efflux pumps were evaluated.

    Results: Among all ETEC isolates, 31/205 exhibited resistance or diminished susceptibility to Nal. Of these 21 (10%) were NalR while 10 were NalI. Only 6 isolates were CipI and none CipR. NalR-CipS strains was the most frequent resistant phenotype detected (17/31, 55%).The most frequent TMQR genes detected were the aac(6′)Ib-cr gene (9/31, 29%), followed by qnrS gene (6/31, 19%). qnrB gene (2/31, 6%) and only one strain to qepA (3%). Thus, 58% (18/31) of the isolates presented at least one TMQR gene. Chromosomal mutations in position 83 of gyrA gene (encoding DNA Gyrase) were detected in 65% (20/31) of the ETEC strains. Of these 18 S-L (17 NalR, 1 NalI) and 2 S-A, both NalI; and none presented substitutions in the parC gene (encoding Topoisomerase IV). Neither the qnrC, qnrD, qnrVC, oqxAB gene were detected. The unusual NalI or NalR phenotype without target mutations in gyrA and parC genes was observed, being detected in 11 isolates (10 NalI + 1 NalR, 35%), in all cases but 3 possessing at least one TMQR. On the other hand, the MIC50 of Nal, when the efflux pump inhibitor was added to the media, a reduction in at least two-fold dilutions was found.

    Conclusion: This study highlights the important role of efflux pumps and the role of the point mutations in gyrA gene in quinolone resistance acquisition. Thus, the development of resistance should be closely monitored.

    Fulton Rivera, MSc1, Anicia Medina, BSc1, Maria Pons, PhD2, Maribel Riveros, BSc1, Joaquim Ruiz, PhD3 and Theresa Ochoa, MD1, (1)Universidad Peruana Cayetano Heredia, Lima, Peru, (2)Universidad Peruana de Ciencias Aplicadas, Lima, Peru, (3)ISGlobal, Barcelona Ctr. Int. Health Res. (CRESIB), Hospital Clínic - Universitat de Barcelona, Barcelona, Spain


    F. Rivera, None

    A. Medina, None

    M. Pons, None

    M. Riveros, None

    J. Ruiz, None

    T. Ochoa, None

    Findings in the abstracts are embargoed until 12:01 a.m. CDT, Wednesday Oct. 26th with the exception of research findings presented at the IDWeek press conferences.