Test can distinguish between viral, bacterial infections

The test can also detect immunity levels in people who have been given the flu vaccine, and detect an infection in the body even before symptoms are felt.

By Stephen Feller

STANFORD, Calif., Dec. 15 (UPI) -- Researchers created a test for differences in gene expression in cells, which can indicate whether a patient's illness is a viral or bacterial infection and may help doctors better select courses of treatment.

The test also can distinguish between influenza and other respiratory infections, as well as tell whether somebody will get sick before they feel symptoms, researchers at Stanford University reported in a new study published in the journal Immunity.


The test looks for specific expression of genes based on a response to a pathogen, which the researchers said could allow the test to measure how well the body is reacting to vaccination and the pathogens present in the body.

"It seems that when there is a viral infection, the immune system turns on a general response to all viruses, followed by a virus-specific response to the particular virus," said Dr. Purvesh Khatri, an associate professor of medicine at Stanford University, in a press release. "You can imagine a decision tree where the immune system asks, 'Is it bacterial or viral?' And if it's viral it turns on the meta-virus signature response. And then it asks, 'If it's viral, which virus is it?' And then it turns on a specialized response for that virus."


The researchers first identified 396 human genes whose expressions change in the presence of a viral infection, a pattern which is different from those of healthy patients or those with bacterial infections. The meta-virus signature pattern can be seen after infection, but before symptoms of illness are apparent.

The second pattern of gene expression the researchers identified looks for a change in 11 human genes and can be distinguished from other viral infections, and bacterial infections. The test can tell both whether a person is building immunity after receiving the flu vaccine or if they are infected with the virus, regardless of the presence of symptoms.

Doctors using the test would be able to tell what a person is infected with and what type of treatment is appropriate, especially in the case of antibiotics to prevent unnecessary usage, Khatri said.

The long term goal, according to Khatri, is to discover broad-spectrum antiviral drugs, similar to antibiotics that can kill a wide range of bacterial infections, for use against infections such as dengue fever.

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