title: Enteroaggregative Escherichia coli: surface protein dispersin increases bacterial uptake of ciprofloxacin.
abstract: Enteroaggregative Escherichia coli (EAEC) causes diarrhoea. The antibiotic of choice for treating EAEC infections is ciprofloxacin. EAEC differs from other subgroups of pathogenic E. coli by having a surface protein, dispersin, which has previously been shown to play an important role in ciprofloxacin susceptibility for EAEC model strain 042. To investigate further the role of dispersin in ciprofloxacin susceptibility, minimum inhibitory concentrations (MICs) were determined for 25 clinical isolates, including 15 with dispersin and 10 without. Dispersin-positive strains had a lower MIC than dispersin-negative strains. The mechanism of action behind this observation may be caused by dispersin (i) increasing the bacteria-antibiotic interaction or (ii) facilitating ciprofloxacin access to the intracellular target, DNA gyrase/topoisomerase. To test the role of dispersin in ciprofloxacin sensitivity, EAEC 042 as well as its isogenic mutants, dispersin mutant (042aap) and a mutant in the transporter apparatus gene aatA, believed to be involved in dispersin transport to the bacterial surface (042aatA), were utilised. As predicted, 042 had a higher sensitivity to ciprofloxacin than 042aap, but it was also found that the MIC of 042aatA was similar to 042aap. To address the question of the role of dispersin in ciprofloxacin susceptibility, the concentration of ciprofloxacin bound in biofilms of 042 and 042aap was quantified by treating bacteria with radiolabelled 2-(14)C-ciprofloxacin. The results showed that dispersin did not increase the amount of bound ciprofloxacin as a function of biomass, indicating instead that dispersin facilitates ciprofloxacin access to the intracellular target leading to increased antibiotic susceptibility.
authors.affiliation: Biological and Nanoscale Systems Group, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; Center for Aerosol and Nanomaterials Engineering, RTI International, Research Triangle Park, NC 27709, USA.
authors.forename: Ninell P
authors.initials: NP
authors.lastname: Mortensen
authors.forename: Nadia
authors.initials: N
authors.lastname: Boisen
authors.forename: Sonia
authors.initials: S
authors.lastname: Carey
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Kennel
authors.forename: Jason D
authors.initials: JD
authors.lastname: Fowlkes
authors.forename: Mitchel J
authors.initials: MJ
authors.lastname: Doktycz
authors.forename: James P
authors.initials: JP
authors.lastname: Nataro
authors.forename: David P
authors.initials: DP
authors.lastname: Allison
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology; D002939:Ciprofloxacin / Q000378:metabolism* / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004927:Escherichia coli Infections / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D055786:Gene Knockout Techniques; D006801:Humans; D008826:Microbial Sensitivity Tests
chemical_list: C479827:AAP protein, E coli; D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D002939:Ciprofloxacin
keywords: Antibiotic susceptibility; Ciprofloxacin; Dispersin; Enteroaggregative Escherichia coli; Radiolabelled