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Marquette Researcher Links Chemical Found in Soap to Antibiotic Resistance

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S Bence
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PhD candidate Dan Carey and Dr. Patrick McNamara inside his Marquette University lab.

A Marquette assistant professor has been making waves with his research into antibacterial chemicals commonly found in soap.

Over the last few months, two studies led by researcher Patrick McNamara were published.  

Study: TCC Influences Antibiotic Resistance, Regardless of Concentration 

One study dug into a common antibacterial ingredient found in bars of soap, triclocarban.   

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A student's notebook

McNamara and his team ran experiments using different concentrations of triclocarban, or TCC.

“We were surprised. We thought that if we had higher levels of triclocarban, we would get more resistance genes. What we found was regardless of concentration, the antibiotic resistant gene increased,” McNamara says. 

According to the CDC, more than 23,000 deaths a year are linked to infections caused by antibiotic resistant bacteria.

While studying at the University of Minnesota, McNamara based his graduate work on a study that investigated the impacts of a different soap additive - triclosan. This synthetically produced antibacterial chemical is a common ingredient in liquid hand soap.   

“If you have a soap that you pump and it says ‘antibacterial,’ chances are it has triclosan. So for a while we thought there was no risk in using triclosan because it’s synthetically produced and it doesn’t have a specific target against bacteria so they’re not going to adapt to it,” McNamara says.   

He says research later disproved the theory.   

“It was found that if bacteria are exposed to triclosan, they can build up tolerance to other antibiotics. Then we did a study two years ago that found out in these mixed cultures... there is a whole slew of bacteria present. When they get exposed to triclosan, they can increase their resistance genes to other antibiotics,” McNamara.   

McNamara says the impact of flushing these chemical down drains and into wastewater treatment plants “is like feeding antibiotics to the treatment plant.”   

“And [triclosan] also got a lot of press because in Minnesota, some researchers found that when triclosan leaves the treatment plant and went into a river, gets exposed to sunlight, it reacts and forms a dioxin, [which are cancer-causing],” he says.   

Study: Promising Process to Remove Antibacterial Chemicals From Treated Sewage Sludge 

McNamara’s second study, funded by the National Science Foundation, found a promising process that can remove TCC and triclosan from treated sewage sludge, or biosolids.   

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In the lab

The process is called pyrolysis. “It is similar to combustion, but there’s no oxygen. So when we heat up the biomass, we make gases like methane, hydrogen that have high-energy content…We thought about pyrolysis since it has high temperatures, it might also get rid of triclosan and TCC that are in biosolids,” McNamara says.   

He says pyrolysis could be incorporated into conventional waste water treatment.   

McNamara says research will continue in his lab.   

“The next step is more the practical side of the research. If we put this reactor in the treatment plant and these chemicals go up into the air, can we catch that air and treat that air basically……we would want to make sure we control that process and ensure that we are completely removing, destroying these chemicals,” McNamara says.   

So, What Can Be Done About This?   

The researcher doesn’t see the chemical being banned anytime soon. But, McNamara says consumers can wield a lot of power through what they choose to purchase.   

“I think of BPA (Bisphenol A) as the most recent hot-button micro pollutant. There were lots of studies that came out about BPA that it’s an estrogen and can be linked to different health issues; should they ban it, could they ban it,” he says. “But what happened was people….stopped buying bottles made of BPA. So when the consumer stops buying a product, they stop making it and in some ways that’s a faster way to get rid of something than to wait for legislation.”

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Susan Bence entered broadcasting in an untraditional way. After years of avid public radio listening, Susan returned to school and earned a bachelor's degree in Journalism from the University of Wisconsin-Milwaukee. She interned for WUWM News and worked with the Lake Effect team, before being hired full-time as a WUWM News reporter / producer.