Using an advanced genetic screening technique, the U.S. Department of Agriculture's (USDA's) Agricultural Research Service scientists have detected--for the first time--over 700 genes that give microbes like Salmonella and E. coli the ability to resist antibiotics and other antimicrobial compounds.

The new screening technique, called DNA microarray technology, allowed scientists to hone in on resistance genes in organisms that pose a threat to public health including: Salmonella, E. coli, Campylobacter, Listeria, and Enterococcus, among others.

USDA scientists expressed worry over the findings, released last week.

"Researchers are concerned that some of these organisms have acquired genetic resistance to the antibiotics used to kill them," said the Agricultural Research Service, the main research arm of the agency, in a statement. "Finding the genes that confer resistance is an important step for scientists looking for new ways to control these organisms."

According to the Agricultural Research Service, all genes identified in organisms are logged into GenBank, a gene database administered by the National Center for Biotechnology Information at the National Institutes of Health (NIH).

A DNA microarray is a small glass slide used to test genetic samples for the presence of specific genes. To use the array, DNA extracted from the bacterium to be tested is tagged with fluorescent dyes and then put into contact with the slide containing DNA probes designed to detect genes that are known to confer antimicrobial resistance.

This work was published in the scientific journal Microbial Drug Resistance.

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