Quick salmonella detection

Detecting salmonella in food has become a relatively simple process. An accurate analysis can be carried out in a laboratory by means of conventional microbiological culture growth techniques. The problem, however, is that the results are obtained within 7 days.

This presents a serious problem for the food industry, which often cannot afford to wait for the results. A manufacturer must therefore decide whether to close down an operation before receiving the results.

At the department of immunology, microbiology and parasitology of the University of the Basque Country (EHU) therefore, it was realised that there was a need to develop more rapid detection systems. As a result, research in the field of genetic techniques was instigated. To this end, contact was made with the company in Alava, Laboratorios Bromatológicos Araba.

Three bodies are now working jointly on this project: the EHU, responsible for the development of a detection system for viable bacteria; Laboratorios Bromatológicos Araba, which applies the university research results to real samples and, finally, the LEIA Technological Centre, charged with developing pre-treatment systems for the samples. The aim of the project is to manage to detect salmonella infection within 24 hours.

Moreover, the fact that the complete genome for salmonella - some 4,500,000 pairs of bases - became known only a few years ago, has provided a great advance for researchers. Although it is too early to talk of results, it has been demonstrated that just a DNA extraction is not sufficient in order to detect salmonella, given that it does not indicate whether the bacteria is alive or dead.

So, with new genetic techniques, other, more specific markers for the viability of the bacteria are being sought. One of these could be RNA.

It is the specific genes just of the salmonella that is the target of this research - some 100 or 200 genes. To this end, a new device that functions much more rapidly has been acquired a PCR that works in real time. This device, moreover, enables the quantifying of the reaction, i.e. it tells us the number of species of salmonella there is. The PCR results are analysed through various graphical representations and then interpreted. The green line indicates the presence of salmonella.

Salmonella is quite a ubiquitous bacterium, found in foodstuffs of animal origin and in contaminated water. It is a resistant micro-organism that adapts easily to extreme environmental conditions. Salmonella actively grows under a wide range of temperatures: less than or equal to 54 degrees Celsius. The consequences are enterocolitis, systemic infections, gastro-enteritis and typhoid fever.