title: Escherichia coli O25b:H4/ST131 are prevalent in Spain and are often not associated with ESBL or quinolone resistance.
abstract: BACKGROUND
  A multiresistant CTX-M-15-producing clonal group of Escherichia coli isolates, namely O25b:H4/ST131, has recently emerged in three continents. At this moment, appropriate studies to assess the real prevalence of this successful lineage are still scarce.
  
  
  METHODS
  In a prospective study in the south of Spain, among all clinical E. coli isolates recovered in Seville during a 30 week period in 2010, ST131 was screened by using PCR for O25b/pabB3/B23 traits. ESBL enzymes were characterized by PCR and sequencing. Genetic relatedness was performed by XbaI PFGE.
  
  
  RESULTS
  This clonal group was found to be prevalent (12.5% of all E. coli isolates), and only 37 (6.8% of ST131 isolates) were ESBL producers. Among 25 characterized ESBL-producing ST131 isolates, 96% harbored CTX-M-15. ST131 isolates were more frequently resistant to amoxicillin/clavulanate, aminoglycosides and fluoroquinolones in both ESBL and non-ESBL producers groups. XbaI PFGE performed on 88 ST131 isolates showed three pulsotypes, which included ≥4 isolates each (25% of all typed ST131 isolates), and 11 pulsotypes, which contained 2-3 isolates each. Three of 14 pulsotypes of this clonal group included both nalidixic acid-resistant and susceptible isolates, and five pulsotypes included both ESBL and non-ESBL producers.
  
  
  CONCLUSIONS
  Our findings suggest that O25b/ST131 is a prevalent clone in our area, and the observed prevalence of ESBL-producers within this clone is similar to that found in the total isolates of this species. Certain pulsotypes among ST131 clone that showed a greater expansion, and ESBL genes acquisition or quinolone resistance could explain part of this prevalence.
authors.affiliation: Microbiology and Infectious Diseases Unit, University Hospital Virgen Macarena, Sevilla, Spain. llopez@us.es
authors.forename: Lorena
authors.initials: L
authors.lastname: López-Cerero
authors.forename: María del Mar
authors.initials: Mdel M
authors.lastname: Bellido
authors.forename: Lara
authors.initials: L
authors.lastname: Serrano
authors.forename: Julia
authors.initials: J
authors.lastname: Liró
authors.forename: Jose Miguel
authors.initials: JM
authors.lastname: Cisneros
authors.forename: Jesús
authors.initials: J
authors.lastname: Rodríguez-Baño
authors.forename: Alvaro
authors.initials: A
authors.lastname: Pascual
mesh_terms: D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology* / Q000302:isolation & purification; D006801:Humans; D011446:Prospective Studies; D015363:Quinolones / Q000494:pharmacology*; D013030:Spain; D001618:beta-Lactamases
chemical_list: D015363:Quinolones; D001618:beta-Lactamases