Bacteriology

Bacteriological research at WFSR is focussed primarily on the four most prevalent pathogens: Salmonella, Listeria, STEC and Campylobacter. We refer to these pathogens as the ‘Big Four’.

Campylobacter: This bacterium causes the most gastrointestinal tract infections in Europe by far. Infection is caused primarily by contaminated food or drinking water, or from contact with infected animals. The origin often lies in inadequate kitchen hygiene and the consumption of raw products.

Salmonella: causes mainly gastrointestinal tract infection, and this is frequently the result of consuming contaminated food. Inadequate heating of food and/or kitchen hygiene is a major cause of Salmonella infections as well. All Salmonella food isolates are classified by serotyping.

STEC: Infection with Shiga toxin-producing Escherichia coli may lead to mild or serious diarrhoea. In a small number of cases (2-7%), the condition deteriorates, sometimes with fatal consequences. Infection with STEC frequently occurs as a result of consuming inadequately heated/cooked meat.  

Listeria: The most important characteristic of these bacteria is that they are able to survive and even grow at low (refrigerated) temperatures. Infection in humans is primarily the result of consuming contaminated food. Most infections are mild, but in the case of those with reduced resistance in particular, the progression of the illness may become extremely serious. At WFSR, we analyse each Listeria food isolate in real time using of Whole Genome Sequencing in order to detect possible outbreaks.

Wageningen Food Safety Research has available a broad arsenal of accredited methods for detecting bacterial contamination. In the classical method, we place food in an environment intended to ascertain whether the specific bacteria will grow. Positive detection often results in a typical bacterial colony on a nutrient medium. Molecular detection methods are used for rapid screening and for identification. Using profiling we are able to investigate whether a detected bacterium is harmful to humans. For this we use gPCR, array techniques, genome sequencing analysis or MALDI, for example. Identification of a bacterial colony can be made within a few minutes by means of a MALDI analysis.

A monitoring programme with the sources that are to be sampled is set up every year by the NVWA. This results in a large quantity of data: how often do we find something, what do we find, where and when? WFSR then has an extensive data set on the basis of which trend analyses and comparisons of food isolates with patient isolates can be carried out. These data are also used by the NVWA for enforcement and risk analyses (risk-based monitoring). If it emerges for example that a particular bacterium occurs too frequently in a product, they can take action in this regard.

Antimicrobial resistance, better known by its abbreviation AMR, poses an increasing threat to public health. A great deal of attention is devoted to this issue in our bacteriological research. We do this in collaboration with Wageningen Bioveterinary Research (WBVR), which conducts research into resistance to antibiotics in animals. Read more on the page AMR.

To analyse a bacterium completely, we also utilise whole genome sequencing of (the DNA of) the bacterium. On this basis, we are able to determine whether it has been found more frequently and how much time passed between the different contaminations. Read more on the page Genomics.