The finding may significantly speed up the response to many outbreaks of foodborne illness, allowing epidemiological investigators to identify the exact strains of Salmonella that make people sick and to more quickly find and eliminate the source of the disease.
“There are more than a million estimated cases of salmonellosis annually in the United States, resulting in approximately 400 deaths, nearly 20,000 hospitalizations and an economic burden of millions of dollars,” said study lead author Nikki Shariat, postdoctoral researcher in molecular microbiology in the Department of Food Science. “Right now, public-health laboratories use a technique called pulse field gel electrophoresis, or PFGE, to subtype Salmonella strains, and it normally takes one to three days to identify a specific strain. The technique we devised often takes just one day.”
The method focuses on two virulence genes and two novel regions of Salmonella DNA called clustered regularly interspaced short palindromic repeats, or CRISPRs. The researchers devised a method of multi-virulence-locus sequence typing, or MVLST, that can detect strain-specific differences in the DNA at these four locations. The researchers designated the method as CRISPR-MVLST.
Shariat explained that the new method is different because it looks at the DNA sequence, whereas the other method basically cuts the DNA into small pieces with no actual sequence information.
“Compared to the current method being used nationally and internationally to subtype Salmonella, our approach is faster,” Shariat said. “The significance of that is you need to trace the source of an outbreak as quickly as you can before you start insisting on restaurant and farm closures. It is important to pinpoint the source of the bacteria — the quicker you do that the quicker you can respond to the disease outbreak.”
The CRISPR-MVLST method also is likely to be much cheaper than conventionally methods, said the researchers. “Additionally, the DNA sequence is basically a text file that is very easy to communicate and share between laboratories nationally and internationally,” Shariat said. “The data is definitely more robust.”
Results of the study were published online in May in the Journal of Clinical Microbiology.
Source: Penn State