title: Characterization of pFOX-7a, a conjugative IncL/M plasmid encoding the FOX-7 AmpC-type β-lactamase, involved in a large outbreak in a neonatal intensive care unit.
abstract: OBJECTIVE
  FOX-type enzymes are a lineage of AmpC-type β-lactamases from Aeromonas spp. whose genes have been mobilized to plasmids spreading among Enterobacteriaceae, where they can be responsible for resistance to extended-spectrum cephalosporins and β-lactamase inhibitor combinations. Little is known about the genetic context and plasmid vehicles of bla(FOX) determinants. Here, we have characterized a plasmid encoding the FOX-7 β-lactamase, which was involved in a large outbreak caused by two Klebsiella pneumoniae clones in a neonatal intensive care unit.
  
  
  METHODS
  Plasmid transferability was tested in conjugation experiments using Escherichia coli recipients. Plasmids from different strains were compared by restriction profiling and PCR mapping. The complete sequence of pFOX-7a plasmid was determined by a next-generation sequencing approach followed by gap filling using PCR and sequencing.
  
  
  RESULTS
  An apparently identical conjugative plasmid encoding FOX-7 was detected in representatives of the K. pneumoniae clones that caused the outbreak and in sporadic FOX-7-producing strains of other species from the same ward. The plasmid, named pFOX-7a, has an IncL/M-type backbone and two separate resistance modules including a Tn3-like transposon and a novel Tn1696 derivative, named Tn6234, which carries an integron platform, a hybrid (but still functional) mercury resistance module and a novel putative transposon of original structure, named Tn6240, associated with the bla(FOX-7) gene.
  
  
  CONCLUSIONS
  pFOX-7a is the first completely characterized plasmid encoding a FOX-type β-lactamase. The bla(FOX-7) gene was associated with a putative transposable element of original structure, which was likely involved in its mobilization from the Aeromonas metagenome.
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Di Pilato
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Arena
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.
authors.forename: Tommaso
authors.initials: T
authors.lastname: Giani
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.
authors.forename: Viola
authors.initials: V
authors.lastname: Conte
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Cresti
authors.affiliation: Department of Medical Biotechnologies, University of Siena, Siena, Italy Department of Experimental and Clinical Medicine, University of Florence, Florence, Italy Microbiology and Virology Unit, Careggi University Hospital, Florence, Italy gianmaria.rossolini@unisi.it.
authors.forename: Gian Maria
authors.initials: GM
authors.lastname: Rossolini
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003227:Conjugation, Genetic; D003428:Cross Infection; D004251:DNA Transposable Elements; D004196:Disease Outbreaks; D023061:Gene Order; D006801:Humans; D032023:Integrons; D007363:Intensive Care Units, Neonatal; D007710:Klebsiella Infections / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000235:genetics*; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics*; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; C048795:AmpC beta-lactamases; D001618:beta-Lactamases
keywords: FOX-type β-lactamase; Gram-negative; class C β-lactamases; transposons