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Super-salmonella can make us smarter

Associate Professor Lotte Jelsbak has discovered a special variant of salmonella, which may be more dangerous than the common salmonella. It is therefore important to study the new variant.
Lotte Jelsbak
Photo: Uffe Weng

Ordinary salmonella can be bad enough, but sometimes special types of the bacteria emerge that can potentially have an even more severe effect on people.

Associate Professor Lotte Jelsbak has discovered just such an example of super-salmonella in her work, which was originally intended to study chronic salmonella. The discovery involves bacteria that is latent in animals, so they do not show signs of being infected. Nevertheless, these animals can cause infection, including in humans. The study should provide answers about why these livestock can infect us with salmonella.

Lotte Jelsbak started with one type of salmonella, which evolved into a different variant. This super-salmonella appears to infect rather easily and is more resistant than the regular bacteria.

“It is normal for changes to occur in the DNA of bacteria. What you might call mistakes in the DNA occur all the time, so that the DNA is constantly changing, and if this error gives the bacteria an advantage in a given situation, e.g. during infection, then a new and more powerful version of the bacteria will emerge. If the error does not produce an advantage, however, the variant will just disappear again” explains Lotte Jelsbak.

Clones with competitive advantage

When a patient has been treated with antibiotics, the patient will be more susceptible to intestinal infections because the antibiotic disrupts the normal intestinal flora, thereby creating room for bacteria that may cause diseases, to grow in the intestine. This also applies to salmonella.

“The special variant we discovered appears to out-compete the normal intestinal flora without prior antibiotic treatment. It is simply better at establishing itself in the gut, and the fact that it can simultaneously cause disease suggests that it is a so-called super-salmonella” emphasizes Lotte Jelsbak.

Bacteria spread rapidly

Valuable new information can be gathered by examining the new variant of salmonella more closely, so we can obtain a greater understanding of how diseases behave.

“There are various types of infectious diseases that are very successful and which spread rapidly and can result in death. Usually, the authorities intervene to try to find the source of such an outbreak so they can stop it. That is the role of the authorities. But it is also important to find out why these types of diseases can do what they do. This is what we as scientists need to investigate” explains Lotte Jelsbak.

The knowledge is important because outbreaks of diseases can develop explosively.

With this new type of salmonella, we can see how little it takes and how rapidly such a bacterium can spread. We have a unique opportunity here to look at which factors come into play. We want to examine how this super-salmonella interacts with normal intestinal flora and how the immune system reacts to it” explains the associate professor.

Better treatment

The knowledge that Lotte Jelsbak hopes to obtain from the ongoing studies of super-salmonella could potentially contribute to the development of improved treatment of salmonella cases using probiotics, which have a different effect than antibiotics.

While antibiotics out-compete and remove the other bacteria in the intestinal flora, probiotics are a type of micro-organisms that have a beneficial effect on the natural intestinal flora in the gut.

The knowledge we produce may also make it possible to develop new probiotics. There is enormous interest in good probiotics” notes Lotte Jelsbak.
The Danish Council for Independent Research – Technology and Production Sciences is funding this project together with a grant from the ‘Aase og Ejnar Danielsens Foundation’.

The bacteria salmonella

Salmonella is a bacterium that is found in and transmitted by animals. Usually, people become infected through meat and eggs, but salmonella can also occur in other foods. In Denmark, salmonella is primarily transmitted through pork, while infection through eggs and chicken is no longer normal.

Salmonella causes gastro-intestinal infections, which may result in diarrhoea, stomach aches, fever, joint and muscle pain and headache.

According to SSI (Statens Serum Institut), there were 925 registered cases of salmonella in 2015, which is the lowest number in the period since 2001. SSI estimates, however, that the real figure is considerably higher, because many of those infected do not go to the doctor with their symptoms.

Sources: Statens Serum Institut and the Danish Veterinary and Food Administration.