Virginia Tech associate professor of civil and environmental engineering Amy Pruden explained that reducing the spread of antibiotic resistance is a critical measure needed to prolong the effectiveness of currently available antibiotics. |
When an antibiotic is
consumed, researchers have learned that up to 90% passes through a body without
metabolizing. This means the drugs can leave the body almost intact through
normal bodily functions.
In the case of
agricultural areas, excreted antibiotics can then enter stream and river
environments through a variety of ways, including discharges from animal
feeding operations, fish hatcheries, and nonpoint sources such as the flow from
fields where manure or biosolids have been applied. Water filtered through
wastewater treatment plants may also contain used antibiotics.
Consequently, these
discharges become “potential sources of antibiotic resistance genes,” says Amy
Pruden, a National
Science Foundation (NSF) Faculty Early Career Development (CAREER) award
recipient, and an assistant professor of civil and environmental
engineering at Virginia
Tech.
“The presence of
antibiotics, even at sub-inhibitory concentrations, can stimulate bacterial
metabolism and thus contribute to the selection and maintenance of antibiotic
resistance genes,” Pruden explains. “Once they are present in rivers,
antibiotic resistance genes are capable of being transferred among bacteria,
including pathogens, through horizontal gene transfer.”
The World Health
Organization and the Center for Disease Control recognize antibiotic resistance
“as a critical health challenge of our time,” Pruden writes in a paper
published in a 2010 issue of Environmental Science and Technology.
Pruden says reducing the
spread of antibiotic resistance is a critical measure needed to prolong the
effectiveness of currently available antibiotics. This is important since “new
drug discovery can no longer keep pace with emerging antibiotic-resistant
infections,” Pruden says.
Pruden who has developed
the concept of antibiotic resistance genes as environmental pollutants has an
international reputation in applied microbial ecology, environmental
remediation, and environmental reservoirs of antimicrobial resistance.
In her work outlined in
the Environmental Science and Technology
article, she and her co-authors, H. Storteboom, M. Arabi, and J.G. Davis, all
of Colorado State Univ., and B. Crimi of Delft
Univ. in The Netherlands, identified
specific patterns of antibiotic resistance gene occurrence in a Colorado watershed.
Identification of these patterns represents a major step in being able to
discriminate between agricultural and wastewater treatment plant sources of
these genes in river environments.
They assert that such
unique patterns of antibiotic resistance gene occurrence represent promising
molecular signatures that may then be used as tracers of specific manmade
sources.
In their study they
identified three wastewater treatment plant sites, six animal feeding operation
locations, and three additional locations along a pristine region of the Poudre River,
in an upstream section located in the Rocky Mountains.
They compared the frequency of detection of 11 sulfonamide and tetracycline
antibiotic resistance genes.
Their findings showed
detection of one particular antibiotic resistance gene in 100% of the treatment
plant and animal feeding operations, but only once in the clean section of the Poudre River.
As they are able to
differentiate between human and animal sources of the antibiotic resistance
genes, Pruden and her colleagues believe they can “shed light on areas where intervention
can be most effective in helping to reduce the spread of these contaminants
through environmental matrixes such as soils, groundwater, surface water, and
sediments.
“This study advances the
recognition of antibiotic resistance genes as sources to impacted environments,
taking an important step in the identification of the dominant processes of the
spreading and transport of antibiotic resistance genes.”
The Colorado Water
Resources Research Institute and a U.S. Department of Agriculture’s Agricultural
Experiment Station provided funding for this study in addition to Pruden’s NSF
award.
