Use of the collections of pathogenic bacteria from the Microbial Resource Centre CIRM-BP to evaluate the antibacterial potential of candidate molecules

International audienceThe International Centre for Microbial Resource dedicated to pathogenic bacteria (CIRM-BP) is located within the French National Institute for Agricultural Research (INRA) centre of Val de Loire. The activity of the CIRMBP is dedicated to the conservation and the distribution of strains of bacterial pathogens isolated from animals or from human as well as the distribution of their genomic DNAs. The CIRM-BP is ISO 9001 certified since 2008. Its collection comprises around 2500 strains belonging to 57 genera and 167 species of bacteria of risk groups 2 and 3. The CIRM-BP offers services related to strain identification, characterization and preservation. The CIRM-BP also develops scientific partnerships for studying biodiversity. Beside these activities, the CIRM-BP takes advantage of its collections of pathogenic strains to study the antibacterial potential of different molecules proposed by its collaborative partners. In that aim, a panel of pathogenic bacterial strains is first constituted considering the intended target for the candidate molecules (for example pathogenic bacteria specific of the production systems of farm animal). This leads to the choice of the bacterial species to be tested and of the strains, in function of their origin and context of isolation

Genomic Comparative Study of Bovine Mastitis Escherichia coli

Escherichia coli, one of the main causative agents of bovine mastitis, is responsible for significant losses on dairy farms. In order to better understand the pathogenicity of E. coli mastitis, an accurate characterization of E. coli strains isolated from mastitis cases is required. By using phylogenetic analyses and whole genome comparison of 5 currently available mastitis E. coli genome sequences, we searched for genotypic traits specific for mastitis isolates. Our data confirm that there is a bias in the distribution of mastitis isolates in the different phylogenetic groups of the E. coli species, with the majority of strains belonging to phylogenetic groups A and B1. An interesting feature is that clustering of strains based on their accessory genome is very similar to that obtained using the core genome. This finding illustrates the fact that phenotypic properties of strains from different phylogroups are likely to be different. As a consequence, it is possible that different strategies could be used by mastitis isolates of different phylogroups to trigger mastitis. Our results indicate that mastitis E. coli isolates analyzed in this study carry very few of the virulence genes described in other pathogenic E. coli strains. A more detailed analysis of the presence/absence of genes involved in LPS synthesis, iron acquisition and type 6 secretion systems did not uncover specific properties of mastitis isolates. Altogether, these results indicate that mastitis E. coli isolates are rather characterized by a lack of bona fide currently described virulence genes

NGS characterization of bovine mastitis <em>Escherichia col</em>i: new insights into diversity and putative virulence mechanisms

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Antibacterial activity of egg albumen during incubation

National audienceThe aim of the present work was to analyse the change of egg white antibacterial activities during egg incubation. Embryonic (E) and unfertilized (U) eggs were incubated for several periods of time, from 0 to 12 days, and the resulting egg whites were analyzed for their pH, protein content and for their antibacterial properties against 5 pathogenic strains. The changes in egg white pH values differed between U and E eggs. Egg white concentrations remained stable during incubation for U eggs but significantly increased for E eggs. At constant protein concentration and for an dentical duration of incubation, egg white activities against Listeria monocytogenes et Streptococcus uberis were similar between E and U groups. A progressive decrease in these activities was however observed depending on the incubation time, regardless of the egg group (U or E). A discrete change in the profile of egg white proteins is also observed during incubation but no difference was noticeable between both groups (E versus U). To conclude, the antibacterial activity of egg white proteins progressively decreased during egg incubation. This observation could result from the alteration of specific antimicrobial proteins. Taken together, these data support that the egg white antibacterial defence is altered during egg incubation, suggesting that new compensatory protection systems might be set up during embryonic development to overcome this apparent weakening

Fraction de protéines et peptides issus du blanc d'oeuf et protéine issue du blanc d'oeuf et leur utilisation comme agent anti-listeria

The invention relates to a fraction of peptides and/or proteins that are derived from egg white and that are capable of binding heparin, for its anti-Listeria monocytogenes action. The invention also relates to a molecule of sequence SEQ ID No. 1 for its antimicrobial action, and in particular anti-Listeria monocytogenes actionL'invention concerne une fraction de peptides et/ou protéines issus du blanc d'œ uf et aptes à lier l'héparine, pour son action anti- Listéria monocytogenes. L'invention concerne également une molécule de séquence SEQ ID n°1 pour son action anti-microbienne, et notamment anti- Listéria monocytogenes

Characterization of egg white antibacterial properties during the first half of incubation: A comparative study between embryonated and unfertilized eggs

International audienceEgg white is an important contributor to the protection of eggs against bacterial contaminations during the first half of incubation (day zero to 12), prior to the egg white transfer into the amniotic fluid to be orally absorbed by the embryo. This protective system relies on an arsenal of antimicrobial proteins and on intrinsic physicochemical properties that are generally unfavorable for bacterial multiplication and dissemination. Some changes in these parameters can be observed in egg white during egg storage and incubation. The aim of this work was to characterize changes in the antibacterial potential of egg white in embryonated eggs (FE) during the first half of incubation using unfertilized eggs (UF) as controls. Egg white samples were collected at day zero, 4, 8, and 12 and analyzed for pH, protein concentration, and protein profile. Antibacterial properties of egg white proteins were evaluated against Listeria monocytogenes, Streptococcus uberis, Staphylococcus aureus, Escherichia coli, and Salmonella Enteritidis. During incubation, differential variations of egg white pH and protein concentrations were observed between UF and FE. At equal protein concentrations, similar activities against L. monocytogenes and S. uberis were observed for FE and UF egg white proteins. A progressive decline in these activities, however, was observed over incubation time, regardless of the egg group (UF or FE). SDS-PAGE analysis of egg white proteins during incubation revealed discrete changes in the profile of major proteins, whereas the stability of some less abundant antimicrobial proteins seemed more affected. To conclude, the antibacterial activity of egg white proteins progressively decreased during the first half of egg incubation, possibly resulting from the alteration of specific antimicrobial proteins. This apparent decline may be partly counterbalanced in embryonated eggs by the increase in egg white protein concentration. The antibacterial potential of egg white is very effective during early stages of embryonic development but its alteration during incubation suggests that extra-embryonic structures could then progressively ensure protective functions

Maximum likelihood phylogenetic analysis.

<p>Analysis was performed on the 5 fully sequenced mastitis strains and 14 additional genomes including those of bovine mastitis model strain P4. The concatenated sequence of the 1976 shared genes were compared under a GTR+I model hypothesis. Branch support are estimated by quartet puzzling (1000 steps). Phylogroups are represented with colored dots. The branch length separating <i>E</i>. <i>fergusonii</i> is not to scale.</p

Presence/absence matrix of genes involved in LPS synthesis.

<p>Presence was analyzed using tblastn (red indicates presence, green indicates absence). Mastitis isolates are in bold characters and underscored.</p

Hierarchical clustering based on the presence of accessory genes.

<p>The binary presence/absence was used to compute the distance among each pair of strains.</p

Presence/absence matrix of genes involved in iron acquisition.

<p>Presence was analyzed using tblastn (red indicates presence, green indicates absence). Mastitis isolates are in bold characters and underscored.</p