ITHACA, N.Y. -- With salmonella-tainted ground turkey sickening more than 100 people and listeria-contaminated cantaloupes killing 15 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, reported online Oct. 14 in the journal Applied and Environmental Microbiology by a collaborative team led by Cornell University scientists, will enable government agencies and food companies to pinpoint the exact nature and origin of food-borne bacteria with unprecedented accuracy, says food science professor Martin Wiedmann.
The standard method of tracing food-borne illness involves breaking up the DNA of bacteria samples into smaller pieces and analyzing their banding patterns.
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.
To surmount this challenge, Wiedmann adopted a genomic approach.
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 -- Wiedmann 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.
In the process of doing so, he also found other links: A Salmonella strain that led to a nationwide recall of pistachio nuts in 2009 turned up in samples from four people -- only one of whom had reported eating pistachios.
|Contact: Joe Schwartz|