New more rapid methods for the detection of salmonella

The food and drink we consume have to pass strict quality control tests. Nevertheless, these precautions are not always sufficient, given that some foodstuffs still give rise to illness. In most cases, food poisoning is caused by micro-organisms. The salmonella bacteria is, without doubt, one of the better known ones. The University of the Basque Country (EHU) is developing a new system to detect salmonella with greater rapidity – within 24 hours.

Salmonella is quite a ubiquitous bacteria, found in foodstuffs of animal origin and in contaminated water. It is a resistant micro-organism which 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 well known to all: enterocolitis, systemic infections, gastro-enteritis and typhoid fever.

Nowadays, detecting salmonella in food is a simple process. An analysis is carried out in the laboratory, by means of conventional microbiological culture growth techniques and the results are obtained within 7 days.

Nevertheless, this gives rise to problems for doctors or for the food industry, not being able to afford this time period and so often finding that they have to make decisions without waiting for or depending on the analysis results. At the Department of Immunology, Microbiology and Parasitology of the EHU, it was realised that there was a need to develop more rapid detection systems and, thus, research in the field of genetic techniques was instigated. To this end, contact was made with the company in Alava (in the Basque Country), Laboratorios Bromatológicos Araba.

Three bodies are 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 or not 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 which 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.