title: CTX-M-15-D-ST648 Escherichia coli from companion animals and horses: another pandemic clone combining multiresistance and extraintestinal virulence?
abstract: OBJECTIVE
  To discern the relevance of ST648 extended-spectrum β-lactamase (ESBL)-producing Escherichia coli as a putative new group of multiresistant and extraintestinal pathogenic strains in animals, its frequency, ESBL types, antimicrobial resistance patterns and virulence gene (VG) profiles should be determined and compared with ST131 strains from the same collection of strains.
  
  
  METHODS
  ESBL-producing E. coli isolates (n = 1152), consecutively sampled from predominantly dogs, cats and horses between 2008 and 2011, were assigned to a phylogenetic group by PCR. Partial multilocus sequence typing was performed for group D and B2 strains and strains presumed to be D-ST648 and B2-ST131 were fully typed. ESBL genes and extraintestinal pathogenic E. coli (ExPEC)-like VGs were characterized by PCR and sequence analysis and antimicrobial resistance was determined by broth dilution. Clonal analysis was done by PFGE.
  
  
  RESULTS
  Forty (3.5%) ESBL-producing E. coli were determined as D-ST648, whereas B2-ST131 isolates occurred less frequently (2.8%). Although the predominant ESBL type in both groups was CTX-M-15 (72.5% versus 46.9%), ST648 strains from companion animals and horses displayed a lower variety of ESBL types (CTX-M-1, -3, -14, -15 and -61 versus CTX-M-1,-2,-14,-15,-27 and -55 and SHV-12). In contrast to ST131 strains, a higher proportion of ST648 strains showed resistance to most non-β-lactam antibiotics. Overall, VGs were less abundant in ST648 strains, although some strains had VG profiles comparable to those of ST131 strains. ExPEC-associated serotype O1:H6 was predominant (46.8%) among the ST648 strains. Some PFGE clusters comprised ST648 isolates from pets, horses and wild birds and humans included from previous studies.
  
  
  CONCLUSIONS
  Our findings demonstrate that certain subgroups of E. coli D-ST648-CTX-M may represent a novel genotype that combines multiresistance, extraintestinal virulence and zoonotic potential.
authors.affiliation: Institute of Hygiene and Infectious Diseases of Animals, Justus-Liebig-Universität Giessen, Frankfurter Str. 85-89, 35392 Giessen, Germany.
authors.forename: Christa
authors.initials: C
authors.lastname: Ewers
authors.forename: Astrid
authors.initials: A
authors.lastname: Bethe
authors.forename: Ivonne
authors.initials: I
authors.lastname: Stamm
authors.forename: Mirjam
authors.initials: M
authors.lastname: Grobbel
authors.forename: Peter A
authors.initials: PA
authors.lastname: Kopp
authors.forename: Beatriz
authors.initials: B
authors.lastname: Guerra
authors.forename: Michael
authors.initials: M
authors.lastname: Stubbe
authors.forename: Yohei
authors.initials: Y
authors.lastname: Doi
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Zong
authors.forename: Axel
authors.initials: A
authors.lastname: Kola
authors.forename: Katharina
authors.initials: K
authors.lastname: Schaufler
authors.forename: Torsten
authors.initials: T
authors.lastname: Semmler
authors.forename: Angelika
authors.initials: A
authors.lastname: Fruth
authors.forename: Lothar H
authors.initials: LH
authors.lastname: Wieler
authors.forename: Sebastian
authors.initials: S
authors.lastname: Guenther
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002415:Cats; D004285:Dogs; D004926:Escherichia coli / Q000145:classification* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D005838:Genotype; D006736:Horses; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D057805:Pets; D010641:Phenotype; D016133:Polymerase Chain Reaction; D037521:Virulence Factors / Q000235:genetics; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D037521:Virulence Factors; C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases
keywords: ESBLs; MLST; antimicrobial resistance