Genetic Screening Technique Can Detect More Than 700
May 26, 2010
Using an advanced genetic screening
Research Service (ARS) scientists and cooperators have detected, for the
first time, more than 700 genes that give microbes like Salmonella and
E. coli the ability to resist antibiotics and other antimicrobial
The researchers used what is called DNA microarray technology to find the
resistance genes in a wide variety of bacteria such as Salmonella,
E. coli, Campylobacter, Listeria, and
Enterococcus, among others. These organisms can cause food poisoning
and are thus a major public health concern.
Researchers are concerned that some of these organisms have acquired genetic
resistance to the antibiotics used to kill them. Finding the genes that confer
resistance is an important step for scientists looking for new ways to control
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. ARS microbiologists
D. Englen, and Richard
J. Meinersmann at the agency's
Epidemiology and Antimicrobial Resistance Research Unit in Athens, Ga.,
along with collaborators at the Sidney Kimmel Cancer Center in San Diego,
Calif., searched through GenBank for genes annotated by other scientists to
likely encode resistance.
Frye and his colleagues selected about 1,000 unique genes from among 5,000
genes found in GenBank that included the words "antimicrobial
resistance" in their description. Then they designed a microarray of more
than 700 DNA probes to detect the resistance genes, according to Frye.
A DNA microarray is a small glass slide used to test genetic samples for the
presence of specific genes. To make the arrays, pieces of DNA called probes are
designed to detect the genes that are known to confer antimicrobial resistance.
These probes are then fused onto the glass slides in specific configurations.
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 the
probes. The antimicrobial-resistance genes in the bacteria will then attach
themselves to the probes they match on the slide, making the specific probe for
that gene fluoresce and thus identifying the antimicrobial resistance gene that
was in the bacterium.
This work was published in the scientific journal Microbial Drug
ARS is the U.S.
Department of Agriculture's (USDA) principal intramural scientific research
agency. This research supports the USDA's priority of ensuring food safety.