Interaction between atypical microorganisms and <i>E. coli</i> in catheter-associated urinary tract biofilms

<div><p>Most biofilms involved in catheter-associated urinary tract infections (CAUTIs) are polymicrobial, with disease causing (eg <i>Escherichia coli</i>) and atypical microorganisms (eg <i>Delftia tsuruhatensis</i>) frequently inhabiting the same catheter. Nevertheless, there is a lack of knowledge about the role of atypical microorganisms. Here, single and dual-species biofilms consisting of <i>E. coli</i> and atypical bacteria (<i>D. tsuruhatensis</i> and <i>Achromobacter xylosoxidans</i>), were evaluated. All species were good biofilm producers (Log 5.84–7.25 CFU cm<sup>−2</sup> at 192 h) in artificial urine. The ability of atypical species to form a biofilm appeared to be hampered by the presence of <i>E. coli</i>. Additionally, when <i>E. coli</i> was added to a pre-formed biofilm of the atypical species, it seemed to take advantage of the first colonizers to accelerate adhesion, even when added at lower concentrations. The results suggest a greater ability of <i>E. coli</i> to form biofilms in conditions mimicking the CAUTIs, whatever the pre-existing microbiota and the inoculum concentration.</p></div>