Antibiotic-resistant bacteria and their genes are abundant contaminants in Iowa waterways, according to new research from the U.S. Geological Survey and the University of Iowa Center for Health Effects of Environmental Contamination.
When humans or animals get sick from bacteria, they’re given antibiotics that fight the infection and prevent further bacterial growth. Sometimes, bacteria can develop resistance to antibiotics, making them difficult or impossible to defeat if they infect hosts again.
In the U.S., more than 35,000 people die from antimicrobial-resistant infections each year, according to the Centers for Disease Control and Prevention.
Those antibiotic-resistant bacteria find their way to waterways — where humans can be exposed to them — through our waste streams, since wastewater treatment doesn’t always get rid them. They can also leach into soil and water bodies from livestock manure that’s spread on fields. Some antibiotic resistance is naturally occurring.
About 85 percent of Iowa’s land is dedicated to agriculture, and the state is dotted with urban hotspots. Those influences have led to bacteria being one of the top impairments of state streams and rivers. That heavy presence made Iowa ground zero for investigating how antibiotic-resistant bacteria moves through the environment.
The resulting study, which was published in the peer-reviewed journal Science of the Total Environment, marked the first statewide assessment of antibiotic-resistant bacteria and genes in Iowa streams.
“There's really a myriad of different sources and ways that it can happen,” said Carrie Givens, the study’s lead author and the environmental microbiology team lead at the USGS Upper Midwest Water Science Center.
“But it’s important for us to understand those patterns and how they persist in the environment, and then how humans can come into contact with them.”
The researchers started the project by determining which Iowa streams they should sample.
They incorporated a spectrum of watersheds -- some with high heavy agricultural presence, some with populated urban areas, and some with little influence from either agriculture and urban areas.
They selected 34 stream locations across Iowa to collect water and sediment samples in 2019. They tried to sample when the waterways were around their normal flow levels and weren’t influenced by rainfall or runoff. They also avoided sampling during agricultural peaks, like when manure was being applied to fields.
Those samples were shipped on ice overnight to the the USGS Organic Geochemistry Research Laboratory in Kansas, where researchers analyzed them for 29 antibiotics and 24 antibiotic-resistant genes. They chose to look for contaminants that are linked to fecal matter and recreational water quality standards, along with antibiotic resistances with the greatest impact to human health.
They found that 68 percent of the waterway samples had enough E. coli to exceed Iowa’s recreational water quality standard, which is a maximum of 235 E. coli organisms per 100 milliliters.
Sign up for the once-a-week Environment & Outdoor Newsletter written by your local environmental journalists Erin Jordan and Brittney J. Miller.
Delivered to your inbox every Thursday
Salmonella growth was detected in 94 percent of water samples and 67 percent of sediment samples.
Antibiotic-resistant bacteria were frequently detected in water samples. Bacteria resistant to the antibiotic vancomycin, used to treat very serious infections, and MRSA bacteria, which cause methicillin-resistant staph infections, were detected in nearly all water samples. Antibiotic-resistant E. coli bacteria were detected in 40 percent of the water samples.
Even when antibiotics themselves weren’t present, researchers still found antibiotic-resistant bacteria in some samples. And the two watersheds without known agriculture and urban influences still showed signs of antibiotic resistance — pointing to its ubiquitous presence in Iowa waterways.
“We definitely don't want to scare anyone from recreating in the water,” Givens said, adding that people with healthy immune systems might only experience mild symptoms if exposed.
“But it's important, if you're going to recreate in these streams ... that you think about recreational advisories that are put forth by your public health agencies.”
The study results provide a baseline understanding of how prevalent antibiotic-resistant bacteria are in Iowa's waterways, highlighting the health risks for humans, wildlife and livestock using these waterways for drinking, irrigating or recreating.
But the team’s investigation into antibiotic resistance in Iowa won’t end with this paper, which took a “snapshot” of Iowa’s water quality at one point in time, said David Cwiertny, the paper’s co-author, director of the UI Center for Health Effects of Environmental Contamination and a UI professor of chemistry and engineering.
The researchers are already working on a follow-up study that explores long-term trends in antibiotic resistance in Iowa streams through about 18 months.
They’re looking at four watersheds: three dominated by agriculture, and one that has high urban influence. They’re taking monthly samples throughout different agricultural seasons and precipitation patterns to track what influences bacteria concentrations.
The team also will try to track some of Iowa’s common bacterial strains back to their sources, whether it be a wastewater treatment plant or a livestock facility.
“We tend to have this really limited discussion about things like beach closures when it comes to bacteria,” Cwiertny said. “We have problems with the bacterial loads in our waters all over the place, not just our beaches.
“We should want to get that out. We should want better than what we have right now.”
www.thegazette.com
When humans or animals get sick from bacteria, they’re given antibiotics that fight the infection and prevent further bacterial growth. Sometimes, bacteria can develop resistance to antibiotics, making them difficult or impossible to defeat if they infect hosts again.
In the U.S., more than 35,000 people die from antimicrobial-resistant infections each year, according to the Centers for Disease Control and Prevention.
Those antibiotic-resistant bacteria find their way to waterways — where humans can be exposed to them — through our waste streams, since wastewater treatment doesn’t always get rid them. They can also leach into soil and water bodies from livestock manure that’s spread on fields. Some antibiotic resistance is naturally occurring.
About 85 percent of Iowa’s land is dedicated to agriculture, and the state is dotted with urban hotspots. Those influences have led to bacteria being one of the top impairments of state streams and rivers. That heavy presence made Iowa ground zero for investigating how antibiotic-resistant bacteria moves through the environment.
The resulting study, which was published in the peer-reviewed journal Science of the Total Environment, marked the first statewide assessment of antibiotic-resistant bacteria and genes in Iowa streams.
“There's really a myriad of different sources and ways that it can happen,” said Carrie Givens, the study’s lead author and the environmental microbiology team lead at the USGS Upper Midwest Water Science Center.
“But it’s important for us to understand those patterns and how they persist in the environment, and then how humans can come into contact with them.”
Methods and results
The researchers started the project by determining which Iowa streams they should sample.
They incorporated a spectrum of watersheds -- some with high heavy agricultural presence, some with populated urban areas, and some with little influence from either agriculture and urban areas.
They selected 34 stream locations across Iowa to collect water and sediment samples in 2019. They tried to sample when the waterways were around their normal flow levels and weren’t influenced by rainfall or runoff. They also avoided sampling during agricultural peaks, like when manure was being applied to fields.
Those samples were shipped on ice overnight to the the USGS Organic Geochemistry Research Laboratory in Kansas, where researchers analyzed them for 29 antibiotics and 24 antibiotic-resistant genes. They chose to look for contaminants that are linked to fecal matter and recreational water quality standards, along with antibiotic resistances with the greatest impact to human health.
They found that 68 percent of the waterway samples had enough E. coli to exceed Iowa’s recreational water quality standard, which is a maximum of 235 E. coli organisms per 100 milliliters.
Want a weekly dose of local environmental news?
Sign up for the once-a-week Environment & Outdoor Newsletter written by your local environmental journalists Erin Jordan and Brittney J. Miller.
Salmonella growth was detected in 94 percent of water samples and 67 percent of sediment samples.
Antibiotic-resistant bacteria were frequently detected in water samples. Bacteria resistant to the antibiotic vancomycin, used to treat very serious infections, and MRSA bacteria, which cause methicillin-resistant staph infections, were detected in nearly all water samples. Antibiotic-resistant E. coli bacteria were detected in 40 percent of the water samples.
Even when antibiotics themselves weren’t present, researchers still found antibiotic-resistant bacteria in some samples. And the two watersheds without known agriculture and urban influences still showed signs of antibiotic resistance — pointing to its ubiquitous presence in Iowa waterways.
“We definitely don't want to scare anyone from recreating in the water,” Givens said, adding that people with healthy immune systems might only experience mild symptoms if exposed.
“But it's important, if you're going to recreate in these streams ... that you think about recreational advisories that are put forth by your public health agencies.”
Next steps
The study results provide a baseline understanding of how prevalent antibiotic-resistant bacteria are in Iowa's waterways, highlighting the health risks for humans, wildlife and livestock using these waterways for drinking, irrigating or recreating.
But the team’s investigation into antibiotic resistance in Iowa won’t end with this paper, which took a “snapshot” of Iowa’s water quality at one point in time, said David Cwiertny, the paper’s co-author, director of the UI Center for Health Effects of Environmental Contamination and a UI professor of chemistry and engineering.
The researchers are already working on a follow-up study that explores long-term trends in antibiotic resistance in Iowa streams through about 18 months.
They’re looking at four watersheds: three dominated by agriculture, and one that has high urban influence. They’re taking monthly samples throughout different agricultural seasons and precipitation patterns to track what influences bacteria concentrations.
The team also will try to track some of Iowa’s common bacterial strains back to their sources, whether it be a wastewater treatment plant or a livestock facility.
“We tend to have this really limited discussion about things like beach closures when it comes to bacteria,” Cwiertny said. “We have problems with the bacterial loads in our waters all over the place, not just our beaches.
“We should want to get that out. We should want better than what we have right now.”
Antibiotic-resistant bacteria infiltrate Iowa waterways, new research finds
It is the first statewide assessment of Iowa streams
www.thegazette.com
