Research Projects

ABSTRACT

In the last ten years, Campylobacter jejuni is the most frequent and increasingly resistant foodborne bacterial intestinal human pathogen, with high costs for public health and economy. New methods and strategies for control of resistant C. jejuni are nedeed, not sensitive to development of new resistance mechanisms. Biological control, with specific biological molecules or live bacterial cells (probiotics) are one of the alternatives. However, interactions of C. jejuni are not understood yet. This project will tackle the gap in fundamental knowledge on C. jejuni interactions on cell-cell, inter-strain and inter-species (C. jejuni-B. subtilis) level. The first aim is to understand quorum sensing (QS) mechanisms and its inhibition by selected plant derived QS inhibitors - we continue previously established work on antimicrobially efficient plant preparations, but quantification of AI-2 signalling molecules – it will be done for the first time with direct HPLC-FLD method. The consequences of QS inhibition will be confirmed in extraintestinal conditions by quantifying adhesion and biofilm on polystyrene and glass contact surfaces and as adhesion and invasion reduction on model cell lines. Concerning inter-strain interactions of C. jejuni, this is the first project studying phylogenetic relatedness of C. jejuni strains in co-culture and impacts on C. jejuni biofilm formation and spread of antibiotic resistance determinants. We predict that more related strains (kin) of C. jejuni are engaged in cooperative behaviour, whereas less related strains (non-kin) are more antagonistic. Co-aggregation, co-adhesion and biofilm formation as well as transfer of resistance of chosen strain combinations will be examined. We will target also C. jejuni-B. subtilis interactions to gain new knowledge of molecular mechanisms behind B. subtilis antagonistic interaction in co-culture and coadhesion (biofilm) assay. Functional role of C. jejuni genes for efflux pumps and stress response as well as B. subtilis genes for antimicrobial compounds and extraintestinal matrix will be confirmed. C. jejuni fitness and biofilm formation dynamics will be determined in the presence of B. subtilis spent medium to understand the importance of direct cell-cell contacts in C. jejuni-B. subtilis interactions. Novel knowledge gained will enable new understanding of B. subtilis as probiotic antagonist of C. jejuni.
With specified project aims we are contributing new knowledge to fundamental science of bacterial interactions which is essential for development new strategies of improved bio-based control of bacterial pathogen – C. jejuni.

THE PHASES OF THE PROJECT AND THEIR REALIZATION

Interactions of C. jejuni will be studied on three levels :
C. jejuni cell signalling inhibition, with the impact on:

1. Changes in growth and survival in conditions of different carbon sources and pH levels;
2. Adhesion and biofilm formation on polystyrene and glass surface;
3. Concentration of the signal synthesis  which will be determiend with quantitative HPLC-FLD analysis;
4. Modulation of virulence (adhesion/invasion on model cell line).

Interstrain interactions of C. jejuni isolates with different genetic background (MLST STs):

1. Merging /boundary line formation between swarms
2. Co-aggregation of strains in liquid media;
3. Co-adhesion on an abiotic model of polystyrene surface and mixed biofilm formation;  
4. Transfer of antibiotic resistance determinants;

Interspecies interactions of C. jejuni and B. subtilis:

1. The role of efflux pumps of C. jejuni in interactions with B. subtilis;
2. The influence of B. subtilis biofilm matrix components and selected antagonistic determinants  in interaction with C. jejuni;
3. The role of cell-to-cell contact in competitive outcomes and the impact of B. subtilis cell free spent medium on C. jejuni biofilm dynamics;
4. The impact of C. jejuni and B. subtilis co-infection and the impact of B. subtilis cell free spent medium on C. jejuni virulence.

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