In a rather special ‘treasure trove’ at Nofima, scientists Birgitte Moen and Even Heir have access to a collection of thousands of strains of bacteria dating back several decades. This enables them to follow how food bacteria develops.

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Anne-May Johansen  

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“Nofima has collected bacteria from food and the food industry over many years, and currently has a strain collection which is worth its weight in gold within the field of research. It allows scientists to study isolates from many decades. In addition, newer technologies such as whole-genome sequencing — determining the entirety of the DNA sequence of a genome — are important tools with which to follow developments in the bacteria and their properties”, says Even Heir, who works in the Department of Food Safety and Quality at Nofima.

Major potential threat

Recently, Nofima’s bacteria collection has once again been used in research. This time in the fight against a major potential threat: Antibiotic-resistant bacteria. Over time, these bacteria may develop resistance so that they can no longer be killed by antibiotics. Parts of the work have involved a collaboration with the Norwegian Veterinary Institute. It is also part of the strategic FutureFoodControl programme at Nofima, where the goal is increased knowledge about safe food, reduced food waste and sustainable packaging systems. The research is funded by the Foundation for Research Levy on Agricultural Products.

The experiments in question focus on Pseudomonas.  This group of bacteria is very widespread and is also dominant in many food and food processing environments.

“There are varieties that cause disease in humans, but the Pseudomonas bacteria we find in food primarily have properties that enable them to survive in food production environments, to be transmitted to food and thus contribute to the deterioration of food, i.e., reduced shelf life, reduced food quality and thus increased food waste”, says Birgitte Moen.

“Therefore, this type of bacteria is a challenge for many food manufacturers. They may pose an even greater challenge if antibiotic resistance is a prevalent trait among bacteria that we find a lot of in both food and food processing environments”, says Even Heir.

Able to survive

From time to time, relatively high levels of antibiotic-resistant E. coli bacteria have been detected in chicken. But what about the Pseudomonas bacterium that causes food to deteriorate?

“This bacterial group has properties that make it even better suited to surviving and growing in food and food production environments, which in turn can increase the spread of both the bacterium and any resistance genes. Pseudomonas in food can therefore be a potential reservoir for the unwanted resistance and spread of resistance genes”, says Even Heir.

In the study, Nofima’s strain collection came into its own and made it possible to identify and compare Pseudomonas bacteria from Norwegian chicken over a period of 26 years.

“We wanted to find out if antibiotic resistance was prevalent among Pseudomonas, whether there had been a development over time and whether the resistance genes we found could be transmissible to other bacteria. Here, whole-genome sequencing was an important tool for detailed mapping of the entire genetic material of the bacteria”, Heir explains.   

Did not find increased resistance

The Nofima scientists found no reason to sound the bacterial alarm after the study was complete. That is good news for Norwegian food manufacturers.

“We found some resistance to some types of antibiotics, but this was entirely expected. Pseudomonas bacteria are well equipped in that they possess a large amount of genetic material, including genes that enable them to survive certain types of antibiotics and cleaning products. But we didn’t find any transmissible resistance. Therefore, the genes cannot be easily transferred between different bacteria”, says Birgitte Moen.

“Nor did we see increased resistance throughout the 26 year period. It is very positive that we didn’t find bacteria with widespread resistance and transmissible resistance genes”, she states.

The Nofima scientists agree that good hygiene in the production facilities and in the kitchen will always be important in reducing the problems and challenges of bacteria in food. This is also important to avoid the spread of resistant bacteria and resistance genes via the food chain.

Favourable position

Antibiotic use in Norway is very low compared to many other countries, so according to Heir, Norwegian food manufacturers are in a favourable position.

“The Norwegian monitoring programme for antimicrobial resistance in animals, food and feed (NORM-VET), coordinated by the Norwegian Veterinary Institute, provides information about the prevalence and development of antibiotic-resistant bacteria. In these reports, we can find out about the levels and development of antibiotic resistance in important types of bacteria in the food chain”, Heir says.

“Can Pseudomonas therefore be acquitted of being a challenging food bacterium in Norway?”

“No! We must pay attention. Pseudomonas is not routinely monitored, and this study is also limited. We cannot rule out that there are other bacteria with transmissible resistance in different parts of the food chain, but the fact that we have isolates of bacteria from decades back allows us to follow developments”, says Even Heir.

Facts about Pseudomonas

Pseudomonas is a genus of bacteria that lives in soil and water.

Pseudomonas are ‘omnipresent’. More than 220 species of Pseudomonas have been documented. It can occur in soil and surface water, in the intestines of animals and humans, and on plants. Among these species, there are variants that can cause serious infections, and are very resistant to antibiotics.

More than ten new species have been identified annually over the past three years, and there is great genetic variation.

Source: Great Norwegian Encyclopedia and Nofima

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