New molecular test can precisely pinpoint food pathogens.

Application of the Single Nucleotide Polymorphism (SNP) for food-borne illness.

With Salmonella-tainted ground turkey sickening more than 100 people and Listeria-contaminated cantaloupes killing 15 persons this year, the ability to detect outbreaks of food-borne illness and determine their sources has become a top public health priority. A new approach, will enable government agencies and food companies to pinpoint the exact nature and origin of food-borne bacteria with unprecedented accuracy.

The standard method of tracing food-borne illness involves breaking up the DNA of bacteria samples into smaller pieces and analyzing their banding patterns (fingerprinting).

But scientists often find that different strains of bacteria have common DNA fingerprints that are too genetically similar to be able to differentiate between them, making it difficult to establish whether the Salmonella that made one person sick was the same Salmonella that infected another person. This was the case in a Salmonella outbreak linked to salami made with contaminated black and red pepper that included 272 cases in 44 states between July 2009 and April 2010.

By sequencing the genome of 47 samples of the bacteria -- 20 that had been collected from human sources during the outbreak, and 27 control samples collected from human, food, animal and environmental sources before the outbreak -- he and his team were able to rapidly discriminate between outbreak-related cases and non-outbreak related cases, isolating four samples believed to be connected to the pepper contamination.

The use of genome sequencing methods to investigate outbreaks of food-borne bacterial diseases is relatively new, and holds great promise as it can help to identify the temporal, geographical and evolutionary origin of an outbreak. In particular, full genome sequence data may help to identify small outbreaks that may not be easily detected with lower resolution subtyping approaches.

Researchers developed the single nucleotide polymorphism (SNP) test that is specific to the 2009 pepper-associated outbreak. A similar approach has previously been used in hospital settings to trace pathogenic bacteria such as methicillin-resistant Staphylococcus aureus, but this is its first application for food-borne illness.

Source: Biology & Nature

http://esciencenews.com/articles/2011/10/25/new.test.can.precisely.pinpoint.food.pathogens

Aporte: Fernando Fuentes Pinochet