Study identifies MRSA in U.S. wastewater treatment plants

A team of University of Maryland School of Public Health researchers recently found that methicillin-resistant Staphylococcus aureus, a potentially fatal superbug, is prevalent at multiple U.S. wastewater treatment plants.

MRSA causes tough to treat and occasionally lethal bacterial infections in patients at hospitals. The bacterium has also infected otherwise healthy people in communities since the late 1990s.

"MRSA infections acquired outside of hospital settings - known as community-acquired MRSA or CA-MRSA- are on the rise and can be just as severe as hospital-acquired MRSA," Amy R. Sapkota, the lead researcher on the study, said. "However, we still do not fully understand the potential environmental sources of MRSA or how people in the community come in contact with this microorganism. This was the first study to investigate U.S. wastewater as a potential environmental reservoir of MRSA."

A Swedish study previously showed MRSA in WWTPs in Sweden and this new study confirms the presence of the bacteria in U.S. plants. The U.S. study found that MRSA and a related pathogen, methicillin-susceptible Staphylococcus aureus, were present in two Mid-Atlantic and two Midwestern WWTPs. MRSA was found in half of all samples and MSSA in 55 percent of samples.

Only one of the plants had the bacteria in the treated water leaving the plant. Chlorination appeared to eliminate all MRSA at the other three.

"Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater," Rachel Rosenberg Goldstein, the study's first author, said. "Because of increasing use of reclaimed wastewater, further research is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater."