Researchers Find High Temperatures Can Kill Superbug Genes

Scanning electron micrograph image of MRSA bacteria (Janice Haney Carr, Centers for Disease Control and Prevention)

New findings by civil engineering researchers at the University of Minnesota in Minneapolis show that treating municipal wastewater solids at higher temperatures can help fight against antibiotic-resistant bacteria. Antibiotics are used to treat bacterial infections, but the growing presence of antibiotic-resistant bacteria — called superbugs — has raised concerns about the future effectiveness of antibiotics.

Much of the focus on combating superbugs, such as methicillin-resistant Staphylococcus aureus (MRSA), has been to find more effective antibiotics. However, civil engineering professor Timothy LaPara took a different approach, namely examining the the treatment of municipal wastewater solids.

Antibiotic resistant bacteria often develop in the gastrointestinal tracts of people taking antibiotics. These bacteria are then passed by the patients and collected by the existing sewer infrastructure and processed through a municipal wastewater treatment facility. The majority of wastewater treatment plants incubate the solid waste, called sludge, in a digester that decomposes organic materials at 95 to 98 degrees Fahrenheit (35 to 37 degrees Celsius).

Lab research by LaPara and his graduate student David Diehl shows that anaerobic digestion of municipal wastewater solids at high temperatures — as high as 130 degrees Fahrenheit or 55 degrees Celsius — is capable of destroying up to 99.9 percent of various genes that confer resistance in bacteria. In contrast, conventional anaerobic digestion, at 95 to 98 degrees Fahrenheit or 37 degrees Celsius, demonstrated only a slight ability to eliminate the same set of genes.

LaPara also pointed out that the added cost of raising the temperature of anaerobic digestion at wastewater treatment plants can be offset because the digesting bacteria produce methane gas that can be used to heat the reactor.

Diehl’s and LaPara’s findings were published in the 9 November issue of the journal Environmental Science & Technology (paid subscription required).

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