title: CTX-M-15-producing Escherichia coli clone B2-O25b-ST131 and Klebsiella spp. isolates in municipal wastewater treatment plant effluents.
abstract: OBJECTIVE
  The global occurrence of antibiotic resistance genes in bacteria in water environments is an increasing concern. Treated wastewater was sampled daily over a 45 day period from the outflow of a municipal wastewater treatment plant in Brno, Czech Republic, and examined for extended-spectrum β-lactamase (ESBL)-producing bacteria.
  
  
  METHODS
  Water samples were cultivated on MacConkey agar with cefotaxime (2 mg/L) and individual colonies were examined for ESBL production. Phenotypic ESBL-positive bacteria identified as Escherichia coli or Klebsiella spp. were tested for the presence of antibiotic resistance genes, the virulence gene afa/dra and the bla(CTX-M) upstream region. Genetic relatedness was analysed by PFGE, multilocus sequence typing and plasmid analysis.
  
  
  RESULTS
  A total of 68 ESBL-producing Enterobacteriaceae isolates were detected in 34 out of 45 wastewater samples. ESBL-producing isolates included 26 E. coli isolates, 4 Klebsiella pneumoniae isolates and 1 Klebsiella oxytoca isolate. The pandemic and multiresistant B2-O25b-ST131 clone was predominant, being detected among 19 E. coli isolates, and 17 of the B2-O25b-ST131 isolates were positive for the FIA replicon and the afa/dra operon and had an IS26 element flanking bla(CTX-M-15). Seventeen of the B2-O25b-ST131 isolates showed closely related PFGE profiles (defined by 84% band similarity) and belonged to identical clonal groups.
  
  
  CONCLUSIONS
  The results highlight the inadequacy of the treatment process in removing multiresistant bacteria from municipal wastewater and point to a risk of transmission of clinically important multiresistant strains, such as the pandemic ST131 clone, to the environment. This is the first study demonstrating the pandemic ST131 clone in wastewater.
authors.affiliation: Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences Brno, Brno, Czech Republic. m.dolejska@centrum.cz
authors.forename: Monika
authors.initials: M
authors.lastname: Dolejska
authors.forename: Petra
authors.initials: P
authors.lastname: Frolkova
authors.forename: Magdalena
authors.initials: M
authors.lastname: Florek
authors.forename: Ivana
authors.initials: I
authors.lastname: Jamborova
authors.forename: Michaela
authors.initials: M
authors.lastname: Purgertova
authors.forename: Iva
authors.initials: I
authors.lastname: Kutilova
authors.forename: Alois
authors.initials: A
authors.lastname: Cizek
authors.forename: Sebastian
authors.initials: S
authors.lastname: Guenther
authors.forename: Ivan
authors.initials: I
authors.lastname: Literak
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods; D003470:Culture Media / Q000737:chemistry; D018153:Czech Republic; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification*; D005838:Genotype; D006801:Humans; D007709:Klebsiella / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification*; D058885:Multilocus Sequence Typing; D010957:Plasmids / Q000032:analysis; D016133:Polymerase Chain Reaction; D037521:Virulence Factors / Q000235:genetics; D014871:Water Microbiology; D018508:Water Purification; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D037521:Virulence Factors; C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases