Unique Activity Spectrum of Colicin F_Y: All 110 Characterized <i>Yersinia enterocolitica</i> Isolates Were Colicin F_Y Susceptible

<div><p>Colicin F_Y is a plasmid encoded toxin that recognizes a yersinia-specific outer membrane protein (YiuR) as a receptor molecule. We have previously shown that the activity spectrum of colicin F_Y comprises strains of the genus <i>Yersinia</i>. In this study, we analyzed the activity of colicin F_Y against 110 <i>Yersinia enterocolitica</i> isolates differing in geographical origin and source. All isolates were characterized through analysis of 16S rRNA genes, serotyping, biotyping, restriction profiling of genomic DNA, detection of virulence markers and susceptibility to antibiotics. This confirmed the broad variability of the collection, in which all 110 <i>Y. enterocolitica</i> isolates, representing 77 various strains, were inhibited by colicin F_Y. Although isolates showed variable levels of susceptibility to colicin F_Y, it was not associated with any strain characteristic. The universal susceptibility of <i>Y. enterocolitica</i> strains to colicin F_Y together with the absence of activity towards strains outside the <i>Yersinia</i> genus suggests potential therapeutic applications for colicin F_Y.</p></div

Identified pulsotypes among <i>Y. enterocolitica</i> isolates.

<p>Similarities (%) between restriction patterns were calculated using the Dice's index and are shown as the numbers close to nodes. The data were sorted using the UPGMA method. For construction of this dendrogram, 41 <i>Y. enterocolitica</i> pulsotypes with similarity lower than 85% were selected from a dendrogram containing all 110 isolates (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081829#pone.0081829.s001" target="_blank">Fig. S1</a>). Susceptibility to colicin F_Y is shown in the right panel, followed by additional strain characteristics. Colicin F_Y titers are shown as the reciprocal exponent of the highest four-fold dilution causing clear (light grey) and turbid (dark grey) zones of inhibition. Subspecies: P =  <i>palearctica</i>, E =  <i>enterocolitica</i>. *Serotypes O:1 and O:2 have been combined to O:3 serotype according to <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081829#pone.0081829-Aleksi1" target="_blank">[1]</a>.</p

Sequence variability between highly and less susceptible <i>Y. enterocolitica</i> isolates.

<p>A) Sequence analysis of YiuR protein from various isolates identified variability in 26 amino acid posistions. B) Sequence analysis of TonB from various isolates identified variability in 18 amino acid positions. A consensus sequence is shown at the top of the figure. The numbers correspond to amino acid position in the YiuR and TonB proteins, respectively.</p