title: Type 3 fimbriae, encoded by the conjugative plasmid pOLA52, enhance biofilm formation and transfer frequencies in Enterobacteriaceae strains.
abstract: The conjugative plasmid pOLA52, which confers resistance to olaquindox and other antimicrobial agents through a multidrug efflux pump, was investigated for its ability to promote biofilm formation in Escherichia coli. Screening of a transposon-mutagenized pOLA52 clone library revealed several biofilm-deficient mutants, which all mapped within a putative operon with high homology to the mrkABCDF operon of Klebsiella pneumoniae, where these genes are responsible for type 3 fimbriae expression, attachment to surfaces and biofilm formation. Biofilm formation in microtitre plates and in urinary catheters of clones containing pOLA52 with a disrupted putative mrk operon was reduced by more than 100-fold and 2-fold, respectively, compared to mutants with an intact mrk operon. The conjugative transfer rate of pOLA52 was also significantly lower when the mrk operon was disrupted. Through reverse transcriptase analysis, it was demonstrated that the genes contained in the putative mrk operon were linked and likely to be expressed as a single operon. Immunoblotting with type 3 fimbriae (MrkA)-specific antibodies further verified expression of type 3 fimbriae. When transferred to other, potentially pathogenic, members of the family Enterobacteriaceae, including Klebsiella pneumoniae, Salmonella Typhimurium, Kluyvera sp. and Enterobacter aerogenes, pOLA52 facilitated increased biofilm formation. pOLA52 is believed to represent the first example of a conjugative plasmid encoding type 3 fimbriae, resulting in enhanced conjugation frequencies and biofilm formation of the plasmid-harbouring strain.
authors.affiliation: Department of Microbiology, University of Copenhagen, 1307 Copenhagen K, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Burmølle
authors.affiliation: Department of Microbiology, University of Copenhagen, 1307 Copenhagen K, Denmark.
authors.forename: Martin Iain
authors.initials: MI
authors.lastname: Bahl
authors.affiliation: Unit for Antimicrobial Resistance, The National Food Institute, DTU, Denmark.
authors.forename: Lars Bogø
authors.initials: LB
authors.lastname: Jensen
authors.affiliation: Department of Microbiology, University of Copenhagen, 1307 Copenhagen K, Denmark.
authors.forename: Søren J
authors.initials: SJ
authors.lastname: Sørensen
authors.affiliation: Department of Microbiology, University of Copenhagen, 1307 Copenhagen K, Denmark.
authors.forename: Lars Hestbjerg
authors.initials: LH
authors.lastname: Hansen
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D002404:Catheterization; D003227:Conjugation, Genetic; D004251:DNA Transposable Elements; D021902:Enterobacter aerogenes / Q000235:genetics; D004864:Equipment and Supplies / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D010861:Fimbriae, Bacterial / Q000235:genetics / Q000502:physiology*; D015151:Immunoblotting; D007711:Klebsiella pneumoniae / Q000235:genetics; D044086:Kluyvera / Q000235:genetics; D016254:Mutagenesis, Insertional; D009876:Operon; D011815:R Factors; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012486:Salmonella typhimurium / Q000235:genetics
chemical_list: D004251:DNA Transposable Elements; D012329:RNA, Bacterial; D012333:RNA, Messenger