New research changes views on food safety

A completely new analysis method has provided answers to why it is that Campylobacter bacteria are able to establish colonies in the intestines of chickens. It turns out that the growth of the bacteria is governed by conditions completely different from what the researchers themselves had believed to be the case.

This article was last updated more than two years ago.


Illness-causing bacteria that may be transferred from animals to humans pose a high risk to our health. Campylobacter is the most common illness-causing bacteria in Norwegian food production, and in the Western world. Among other places, it is found in chicken, where it grows in the intestines of chickens. The bacteria are transferred to the meat during the slaughtering process. People who eat chicken with a lot of Campylobacter bacteria that has not been sufficiently heat-treated become ill. Nearly 5 % of all Norwegian fryers are infected with Campylobacter, according to figures from the National Veterinary Institute of Norway. The figure has risen slightly from 2005 to 2006.

"The consequence is that we must think differently in order to gain the upper hand with Campylobacter in food," says researcher Knut Rudi of Matforsk.

Different background – similar development

A group of researchers in several Nordic countries have studied the dynamics of the colonization of chicken intestines by seven strains of Campylobacter. They also analysed it with respect to two different background flora in the intestines. "The background flora were completely different, but the patterns for the development of the bacteria were extremely similar. This indicates that it is the chicken itself, and not the flora in the intestines, that is the key to fighting Campylobacter. This goes against what people had believed up to now," says Research Fellow Beate Skånseng of Matforsk.

Revolutionary method

The most astounding thing about the findings is, nevertheless, not precisely what determines the growth of the bacteria, but rather how it was figured out. The researchers at Matforsk have developed a new method that makes it possible to determine which strains of bacteria will grow and survive in the intestines without first growing the bacteria.
"It is completely revolutionary. Think of the E. coli outbreak in Norway in the winter of 2006 and how hard they worked in order to find the right strain," says Knut Rudi.

Suitable for all bacteria

The DNA-based analysis method has sequenced one gene from each of the different Campylobacter strains. This requires that one be familiar with the mutations of the different strains. "The method can be used for all known strains of bacteria for which we know the mutations," says Beate Skånseng.
"Studying multiple-strain infections will also be important for other illness-causing bacteria, in order to learn have we can fight them," she concludes.

Immune response of chickens

Microbiologists had a theory that other bacteria in the intestines could outcompete Campylobacter, and that the presence of other, "good" bacteria was important to suppress the growth of Campylobacter colonies. This turned out to be incorrect. Instead, it is probably the chicken itself that affects its own bacterial flora. The chicken’s immune response (the manner by which it recognizes and fights an illness-producing bacteria) is the crucial factor. "Chickens that are infected by Campylobacter do not become ill, but rather have an immune response similar to the one humans also have. This response has not been emphasized earlier. But now it turns out that this is the most critical factor, because it determines the growth of the bacteria in the intestines," explains Knut Rudi.

Made an error

"We have expended a great del of resources in finding other bacteria that were able to outcompete Campylobacter. Finding such protective bacteria was what we were originally given money for. However, the interpretation of the data showed quite clearly that other bacteria were of no significance," says Rudi. It also showed that these bacteria, similar to many others, are extremely able to adapt. As quickly as we have found ways of removing individual types, new types start spreading. The researchers themselves were of the belief that if you could just manage to keep Campylobacter to a minimum, then it was not so dangerous if the bacteria were to be found in certain environments. "We were wrong," admits Knut Rudi.

Interdisciplinary success

The new analysis method was not the only thing needed to solve the Campylobacter riddle. The DNA analyses were connected up with competence in multivariate statistics, which is one of Matforsk’s core competency areas. Knut Rudi is of the opinion that it is important to see the value of new professional connections in the work with food safety, which is continually becoming more important, but also more complicated. "It is only through non-traditional connections that we have been able to attain these results. It shows that we cannot lock ourselves into a theory or an approach. In this case the answer in fact turned out to be the opposite of what we had believed," says Rudi.

New article

Rudi and Skånseng have written an article on the findings that is published in the high-profile American scientific journal PLoS Pathogens. This periodical is open source. In other words, everything that is published there may freely be used by others. "For us, it is important to stick our necks out and use the newest publication channels," says Rudi, who is obviously quite pleased.

 Food safety and quality  

Related content