Category Research project
  • Mikrobiologie

PAC-Campy - Horizontal gene transfer as factor for enhanced fitness

Project status
Completed
Project start
Sept 2017
Project end
Aug 2020
Acronym
PAC-Campy
Department
Biologische Sicherheit
Website
http://www.bfr.bund.de/de/start.html

Description and Objective

Campylobacter is a major cause of acute bacterial enteritis in humans and causes a high economic burden in industrialized nations worldwide. In addition, immunological sequelae of infections such as the Guillain-Barré-Syndrome or chronic arthritis account for serious suffering. The increasing number of officially registered human cases creates the urgent need for development of novel strategies for prevention, control and treatment of Campylobacter infections. To achieve this, we are proposing several coordinated lines of research within this closely linked One Health consortium represented by veterinarians, food microbiologists, physicians, epidemiologists, micro-biologists, public health experts and basic researchers. We aim to use the cooperative power of this network to investigate the efficacyPositive Predictive ValueTo glossary of mitigation strategies established along the food chain, survival strategies outside the host and host-pathogen interaction in order to limit pathogen colonisation and spread in affected animals, in humans and in the environment, respectively. In line with investigations of virulence, genetic exchange, epidemiology, transmission and survival, these measures will provide novel strategies to prevent and combat both, Campylobacter colonisation in chickens as well as human infections. Another major focus is set onto the development of novel molecular methods that will allow for sensitive quantitative detection of Campylobacter spp. at all stages of the food chain. Finally, models of risk intervention and improved source attribution, based on data generated by the consortium, will support public health authorities and industry to focus intervention measures accordingly.

Result

Genetic exchange, especially natural transformation, in which bacteria take up free DNA from the environment, can lead to a high adaptive potential and thus to an enhanced survival of Campylobacter in the environment. In a screening, Campylobacter isolates were observed with ambiguous species differentiation by quantitative real-time PCR. These isolates were analyzed by whole genome sequencing. It turned out that these strains were Campylobacter coli with substantial sequence introgression from C. jejuni. These strains shared a common set of genes with C. jejuni sequences. The gene products may function in stress response. The results have impact on interpretation of routine species differentiation. The immense transfer of genetic material between different Campylobacter species underscores the need to consider genetic adaptability while developing reduction strategies for Campylobacter on poultry meat. This is important to sustainably reduce the pathogen on poultry carcasses. The classical approach to study natural transformation is time-consuming and labor-intensive. Additional factors may bias the final result. Therefore, during the first funding phase of this project we established an assay to visualize DNA uptake at single cell level using fluorescently labeled DNA. Consequently, for the first time we were able to analyze putative stimulating or inhibiting factors of DNA uptake. A slight acidic pH led to drastically reduced competence development and DNA uptake. These findings are complementary to the use of organic acids in drinking water tested by project IP5 to reduce colonization of Campylobacter spp.. In order to suggest targeted reduction strategies in the future it is important to better understand the process of DNA uptake. Therefore, mutants with potential defects in natural transformation were generated. Mutants were tested for their ability to take up free DNA using the established DNA uptake assay. In particular, genes were inactivated that potentially play a role in the direct transport of DNA across both membranes of the Gram-negative bacterium using antibiotic insertion cassettes. Mutants were generated that were not able to take up labeled DNA across the outer membrane into the periplasm and were also not transformable with a classical selection marker. As expected, a mutant lacking the gene for the structural unit of the inner membrane transporter did not show reduced DNA uptake into the periplasm. Further transport of DNA was not possible and therefore no transformation activity was observed. The findings are valuable in that they increase the understanding of Campylobacter spp. genetic exchange and highlight potential steps for inhibition of natural transformation that, in combination with the application of reduction strategies, may improve their sustainability in the future.
Type of project

Third-party funded project

Research focus

Gesundheit von Mensch, Tier und Umwelt (One Health)

Organisational units and partners

Lead specialist group: Lebensmittelmikrobiologie, Erreger-Wirt-Interaktionen (42)
Contact persons: Dr. Kerstin Stingl
External partner: Freie Universität Berlin, Charité - Universitätsmedizin Berlin, Stiftung Tierärztliche Hochschule Hannover, Friedrich-Alexander-Universität Erlangen-Nürnberg , Robert Koch-Institut, Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, Institut für Lebensmittelsicherheit und -hygiene, Mikrobielle Genomik, Institut für Tier- und Umwelthygiene

Funding body and grant number

Bundesministerium für Bildung und Forschung
Förderkennzeichen des BMBF: 01KI1725B

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