Each year, there are nearly three million cases of antibiotic-resistant infections in the U.S. caused by MRSA and other antibiotic-resistant bacteria, according to the Centers for Disease Control and Prevention. While many of these infections happen during hospital stays, less is known about the role wastewater treatment facilities can play in the spread of antibiotic-resistant bacteria in the environment.
Researchers at Oregon State University aim to change that with a new study that launched this month. They were awarded more than $2 million from the Environmental Protection Agency to study the presence of antibiotics, antibiotic-resistant bacteria and their genes at 40 wastewater treatment facilities in the U.S., including Oregon. The two-year-long study will also look at seasonal and regional differences in the population of that bacteria and how different treatment processes affect their growth and evolution.
Joining us to share details of the study is Tala Navab-Daneshmand, the principal investigator of the study and an associate professor of engineering at OSU.
Note: The following transcript was created by a computer and edited by a volunteer.
Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. Nearly three million Americans get antibiotic resistant infections every year. While many infections happen during hospital stays, less is known about the role that wastewater treatment facilities can play in the spread of these bacteria in the environment. Researchers at Oregon State University want to fill in some of those blanks. They recently got more than $2 million from the Environmental Protection Agency to study the presence of antibiotics and antibiotic-resistant bacteria at 40 wastewater treatment facilities all across the U.S.
Tala Navab-Daneshmand is an associate professor of engineering at OSU and the principal investigator of this study. She joins us now. Welcome to Think Out Loud.
Tala Navab-Daneshmand: Thanks for having me.
Miller: How is it that wastewater treatment plants can become reservoirs for antibiotic resistant bacteria?
Navab-Daneshmand: Well, municipal wastewater is one of the main sources of antibiotics and antibiotic-resistant bacteria and genes. That comes from what we flush down the toilet usually but also from the runoff from agricultural fields.
Miller: So when you say the toilet, meaning, we are flushing down all kinds of bacteria in our waste but also antibiotics in our waste as well?
Navab-Daneshmand: Yes. So when we consume antibiotics, there are residuals that leave our body and enter through the urine and enter the wastewater.
Miller: And some of them, even by the time they go through the sewer and get to a treatment plant, some of the antibiotics can still have antibiotic properties and still exert pressure on bacteria?
Navab-Daneshmand: Yes. The wastewater treatment processes, there are several different segments in a wastewater treatment plant. Usually wastewater goes in some of the … like there is some physical treatment when some of the big debris, for example, are removed. Then in biological treatment units, what we call bacteria work to degrade the contaminants. That could be chemicals like antibiotics and other organic contaminants, and also work on removing, reducing microorganisms, bacteria in wastewater. But then the liquid portion of the wastewater goes through disinfection. And then it enters waterways like rivers or is used for irrigation. However, not everything is removed and there are residuals, contaminants such as antibiotics and bacteria in what leaves the wastewater treatment plant.
Miller: Well, that’s a key point here because I was going to say, why does this matter if it’s all eventually getting taken care of? But you’re saying that even some of the cleaned water when it leaves these treatment plants, it can still have both antibiotics in it as well as bacteria?
Navab-Daneshmand: Yes, because there are guidelines and wastewater utilities that follow these standards and guidelines. But the guidelines, what they stipulate are based on human health risk assessments that have been done. The guidelines that we follow though, don’t control for antibiotics or antibiotic-resistant bacteria. They control for target fecal indicators, so target bacteria. For example, you might have heard of E. coli as a bacteria that we hear about for contamination on like lettuce recalls or produce recalls, where there is increased contamination. So as utilities, they control for those regulated contaminants. There are also, for example, regulations for heavy metals. However, there are no regulations for antibiotic or antibiotic resistant bacteria.
Miller: If you were going to design, in a kind of evil way, a system that was engineered to be most likely to create antibiotic-resistant bacteria, it seems like putting antibiotics in a place where there is tons of bacteria, a place full of sewage, that’s not a bad way to do it.
Navab-Daneshmand: Yeah. You put all these things together, exactly. And that’s why wastewater treatment utilities are one of the reservoirs and sources, but also a bridge to the environment. They do reduce a lot of contaminants. But we also need to understand what happens when they are there together. What are some of the things that are increasing and the contaminants that are basically, yeah, being produced in the unit?
Miller: Just to be clear, we haven’t mentioned the specific mechanism yet, but the basic idea – and please correct me if I’m wrong – my layman’s understanding here is that the reason this is a concern is that some bacteria through selective pressure, it turns out they can survive the antibiotics. And then if we get that bacteria and if it’s one that actually can make people or livestock sick, then by definition, the antibiotics that we currently have are less likely or not likely to work on them. That’s why this is a concern.
Can you actually track bacteria from a farm or in human outbreaks to bacteria that came from a wastewater treatment program or facility?
Navab-Daneshmand: That’s a good question. I would say we have fecal indicators and a lot of them are associated with clinical bacteria. So they have clinical traits. For example, when we look for certain targets, we might be able to say, yeah, this is a human sourced target. Whereas some resistances we observed are not associated with human antibiotics, but more with some animal farms, for example, or they are using agriculture. So yes, there are some indicators that we can connect them to humans or animals or other sources.
Miller: So let’s turn to this big new project with over $2 million of federal funding. What’s the big question that you hope to answer?
Navab-Daneshmand: The overall objective of our project is to improve our understanding of the nature, the extent, and the selection and removal of antibiotics and antibiotic-resistant bacteria in wastewater systems. So there are two main aspects to this project. We want to understand how antibiotic resistance is distributed nationwide in municipal wastewater, accounting for seasonality, variations in regions, in demographic information. We also want to know, get a better understanding, with this large-scale nationwide study, on how different wastewater treatment processes impact antibiotic resistance. Are there some processes that remove, reduce antibiotic resistance better than the other ones?
Miller: Well, how much variation is there in the way wastewater treatment plants operate, community to community, state to state?
Navab-Daneshmand: There are different processes. So the biological treatment unit that I mentioned earlier, there are a variety of different processes, these different designs that the way water treatment utilities can use. And therefore, like there is activated sludge, there is lagoons … lagoons are more like ponds that smaller communities have. There are advanced treatment processes that some utilities have. So understanding which one, and some of these processes also just have slight differences from one another in terms of maybe the temperature. So some of the differences are small and some of them are just different units. And this is important because when utilities are going through renovation, they want to do some updates, our hope is that our study can inform those decisions.
Miller: How much variation is there in the use of antibiotics from community to community?
Navab-Daneshmand: There is some evidence, some studies that have shown, in terms of antibiotic consumption, more inappropriate prescription. And when I say inappropriate prescription, it’s when you have an infection but maybe it is not a bacterial infection, and therefore antibiotic is not the right treatment. And so there are some reports showing inappropriate antibiotic prescriptions are higher amongst Hispanic and Black patients. There are some studies that have shown evidence that are increases in antibiotic resistance when in communities with increases in poverty, age, or belonging to U.S. ethnic and minority racial class.
Miller: So what exactly are you going to have all of these communities or all of these facilities test for?
Navab-Daneshmand: We are going to collect samples. And how that would look like, we’re going to send coolers, large coolers with bottles for sample collection with instructions, across the nation, to the utilities that are participating in our study, and they will collect the samples as we instruct them from different point sources on their different points in their utility treatment train, from the beginning. So the raw sewage that comes into the utility, and then before and after each treatment unit. And then what goes out of the utility. Then they ship all those samples to us on ice because we’re looking at bacteria, so we want to have ice there, so we keep the temperature low and things don’t change by the time they reach us. Then we test those in our lab. We have, in addition to me, there are three other collaborators from Oregon State that are participating in this study, that are collaborating, and we work together to quantify antibiotic-resistant bacteria, antibiotic-resistant genes and antibiotic compounds in those samples.
Miller: Does your lab smell?
Navab-Daneshmand: Oh, yeah. [Laughter]
Miller: I assume … I mean, you’re dealing with raw sewage or treated sewage at various stages of treatment over time.
I’m curious, one issue is that potentially dangerous bacteria are always evolving and sometimes gaining new levels of resistance. Is it difficult to even know what to look for?
Navab-Daneshmand: Well, it is getting better and better, and that’s one of the things our project is going to highlight. When I started working on antibiotic-resistant topic about eight years ago at Oregon State, there weren’t really any indicators. There were a lot of targets that we were quantifying, and more and more with time, globally, there are more agreed upon targets to look for. When we talk about general fecal indicator bacteria, like I mentioned E. coli earlier, that’s a pretty agreed upon global target. In terms of antibiotic resistance, in the past couple of years, there are reports and our study is aiming to use those reported recommended targets and then report back to the scientific community about the results. And basically, how well these targets are working when we quantify them across different regions in a large scale study.
Miller: With the hope that eventually the most effective treatments that reduce the prevalence of antibiotic-resistant bacteria, those could be more widely used around the country?
Navab-Daneshmand: Yes.
Miller: Tala Navab-Daneshmand, thanks very much.
Navab-Daneshmand: Thanks for having me.
Miller: Tala Navab-Daneshmand is an associate professor of environmental engineering at Oregon State University.
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