Tim LaPara points to wastewater—and our treatment of it—as the culprit in antibiotic resistance
Animated in conversation and passionate about his research, Tim LaPara is the kind of professor who’s not afraid to speak his mind or tackle conventional wisdom. Groundbreaking and challenging also applies to his research in the University of Minnesota’s department of civil engineering, where he examines the relationship between wastewater treatment and microbial ecology.
An environmental engineer and professor in the Water Resources Science program, LaPara investigates how infrastructure can protect public health and the environment. His recent work has zeroed in on the most pressing threat to modern medicine—the rise of antibiotic resistance in the environment.
“The current scientific paradigm is that antibiotic resistance is primarily caused by overuse of antibiotics, a theory which has led to initiatives to restrict antibiotic prescriptions and curtail antibiotic use in agriculture,” says LaPara, who calls the recent push to limit the use of antibiotics in humans and animals “toothless” and one that doesn’t address the problem at its source.
LaPara, instead, has turned the approach to the crisis on its head: “Poop is the real problem, or more specifically, our treatment of it,” he says.
Even the most state-of-the art municipal wastewater treatment facilities are a major source of antibiotic resistant bacteria entering the environment, says LaPara. “Getting rid of antibiotic resistant genetic material at the wastewater treatment level is a new way of thinking about the problem, it’s a totally different paradigm.”
Antibiotic resistant bacteria develop in the gastrointestinal tracts of humans and animals taking antibiotics. The bacteria are shed through defacaection, most of which are collected by sewers connected to wastewater treatment facilities. Plants treat the sold waste portion of wastewater—called sludge—with anaerobic digestors powered by methane that raise the temperature of solid waste to 95 to 98 degrees.
“The trouble is, the current treatment process is too close to body temperature, the perfect environment for antibiotic resistant bacteria to survive and even grow,” LaPara says. While the liquid portion of the treated water is released in lakes and rivers, the majority of treated sludge ends up in landfills or in agricultural fields as fertilizer.
LaPara’s research found that exposing municipal wastewater solids to higher temperatures – to at least 130 degrees—destroys the genes used by the bacteria to develop resistance. Current technologies result in bacteria having a half-life in the order of a few days to a few weeks; LaPara’s research shows that heating sludge to 120-140 degrees results in a half-life of a few hours.
Retrofitting wastewater treatment plants to raise the temperature of digestion enough to kill the antibiotic resistance would be relatively easy and inexpensive to do, LaPara says. The infrastructure is already in place, as most wastewater treatment plants use self-generated methane gas to heat the sludge. While he’s optimistic that down the road, public health issues coupled by environment concerns will pressure change in the wastewater superstructure, he says, “Inertia is definitely a problem.”