Gene-based Test IDs Listeria Infection
December 2005
Scientists from SRI International have discovered a set of genes associated with Listeria infection in mice. By measuring the expression of just eight genes in liver, the team was able to diagnose mild and severe disease, just six hours after infection, paving the way for rapid new molecular diagnostics.
Listeria monocytogenes is a food-born bacteria which kills hundreds of people in the US every year, primarily pregnant women, infants and immunocompromised patients. Prompt treatment with antibiotics can prevent many of the serious effects of Listeria infection, but early diagnosis is critical; conventional tests can take up to 48 hours for the bacteria to grow before a diagnose can be made. Scientists now hope to detect the disease just a few hours after infection by looking for changes in human gene expression that occur in response to Listeria.
In a study published in the December 2005 issue of Genomics, scientists led by Dr. Hanna Ng used Affymetrix U74Av2 microarrays to discover more than 125 genes that were differentially expressed in mouse liver following Listeria infection; many of the genes were involved in acute or immune responses, cell migration and cell death.
The team infected mice with two doses of bacteria, enabling them to track gene expression changes associated with mild and severe infection. By focusing on just eight of the most highly affected genes in the liver, the researchers correctly diagnosed healthy mice, modestly-infected mice and lethally-infected mice over 90 percent of the time. By testing blood in 40 mice for a different set of 14 genes, the group correctly diagnosed degree of infection 80 percent of the time. Moreover, they were able to diagnose disease just six hours after infection, proving that a blood test based on a small number of genes is a viable prospect for the future.
While Ng studied mice, her research provides the first global gene expression profiling of how an organism responds to Listeria infection using whole-genome microarrays. Testing for changes in host gene expression in response to Listeria infection, especially from an easily-accessed fluid like blood, sets the foundation for developing a rapid gene-based diagnostic to screen at-risk populations and catch the infection before it's too late to treat.
