Salmonella DNA test returns faster results

By George Reynolds

- Last updated on GMT

Related tags: Human salmonella infections, Dna, Salmonella

A new salmonella detection system that uses genetic profiling to
analyse food samples could slash result times, claim researchers.

Salmonella is one of the food industry's most problematic food-poisoning pathogens. Eggs, poultry meat and pork are the major sources of human Salmonella infections. Conventional microbiological techniques can take up to week, resulting in either costly delays in processing plants or expensive recalls if perishable foods shipped prior to result confirmation are found to be contaminated. Researchers with the University of Basque Country in Spain, claim the new system can detect and return results of salmonella contamination within 24 hours. Several strains of Salmonella have been totally sequenced by scientists and so the genetic make up of some bacteria can be specifically tested for their presence. Certain genes are unique to salmonella or are not found in any other living matter. Reducing what the system is searching for reduces the time in which results can be confirmed, the scientists said in revealing details of their work. However, the drawback of conventional testing of deoxyribonucleic acid (DNA) is that it is stable and therefore present even when the harmful bacteria is destroyed using pasteurisation or sterilisation. University researchers claim to have found another, more specific marker for detecting of the active bacteria. The new system looks for messenger ribonucleic acid (RNA), which is an unstable and easily degradable molecule and only produced when the bacteria is active. With this knowledge, the researchers have designed a procedure to extract this RNA from food samples. Once an RNA sample is taken, it is transformed into DNA by means of inverse transcription. This process results in the DNA copy being created, which is then detected by probes previously developed by the University. The probes are DNA chains that are complementary to Salmonella genes marked with a fluorescent compound. According to the researchers, if the DNA copy and the complementary DNA unite, the fluorescent compound emits a signal detectable in real time. The device also enable quality controllers the number of Salmonella cells present in the food sample. According to a European Commission study published in 2005 there were 192,703 reported cases of salmonellosis, the human illness caused by salmonella, during 2004 in the EU's then 25 member states.

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