Pseudomonas aeruginosa produces three different types of bacteriocins: the soluble S-pyocins and the bacteriophage-like F-and R-pyocins. R-pyocins kill susceptible bacteria of the same or closely related species with high efficiency. Five different types of R-pyocins (R1-to R5-pyocins) have been described based on their killing spectra and tail fiber protein sequences. We analyzed the distribution of R-pyocin genes in a collection of clinical P. aeruginosa isolates. We found similar percentages of isolates not containing R-pyocins (28%) and isolates containing genes encoding R1-pyocins (25%), R2-pyocins (17%), and R5-pyocins (29%). The R-pyocindeficient isolates were susceptible to R1-, R2-, and R5-pyocins, while most R2-and R5-pyocin producers were resistant. Determination of the O serotypes revealed that the R-pyocin-susceptible isolates belonged to serotypes O1, O3, and O6, while the R-pyocin-resistant isolates were serotype O10, O11, and O12 isolates. We hypothesized that O-serotype-specific lipopolysaccharide (LPS) packaging densities may account for the distinct accessibilities of R-pyocins to their receptors at the cell surface. Using genetically defined LPS mutants, we showed that the L-Rha residue and two distinct D-Glc residues of the outer core are part of the receptor sites for R1-, R2-, and R5-pyocins, respectively. To illustrate R-pyocin-mediated intraspecies biological warfare, we monitored the population dynamics of two different R-pyocin-producing P. aeruginosa clones of sequential respiratory isolates obtained from a colonized patient. The results of this study highlight the potential role of R-pyocins in shaping bacterial populations during host colonization and support use of these molecules as specific and potent bactericidal agents.

This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

No abstract

No abstract

Le genre Campylobacter comprend plusieurs espèces pathogènes pour l'homme, en particulier C. jejuni, C. coli et C. fetus. C. jejuni et C. coli sont responsables d'entérites généralement spontanément résolutives chez l'individu sain, et peu fréquemment associées à des bactériémies. C. fetus est un pathogène méconnu, rarement identifié dans les échantillons fécaux mais parfois retrouvé dans des hémocultures, en particulier chez des patients présentant des comorbidités ou immunosupprimés. La bactériémie à C. fetus se distingue par son association avec des infections endovasculaires et des foyers infectieux profonds sans symptomatologie digestive. Invasive Campylobacter infections Campylobacter genus encompasses many species, among which C. jejuni, C. coli and C. fetus are the main human pathogens. C. jejuni/coli frequently cause self-limited enteritis in immunocompetent hosts and are seldomly associated with bacteriemia. C. fetus is less common as a human pathogen. It is rarely identified in fecal samples but can sometimes be isolated in blood samples from patients with comorbidities or immunosuppression. Campylobacter fetus bacteriemia is remarkable since it is associated with endovascular and deep-seated infections.