MRSA found in U.S. wastewater treatment plants, study shows

6 Nov

Methicillin-resistant Staphylococcus aureus (MRSA) has historically been associated with hospitals, and been the culprit of potentially fatal bacterial infections. But, since the latter part of the 90s, the infection has spread to community settings such as gyms and schools and has infected healthy people. As MRSA became more prevalent in humans and communities, it became resistant to common antibiotics such as penicillin.

But, now the “superbug” has been identified in wastewater treatment plants in the U.S. The water from these plants is often reclaimed and used for irrigation, causing the researchers of the study to call their findings a “public health concern.”

The study was conducted by researchers at the University of Maryland School of Public Health. The team obtained water samples from two Mid-Atlantic and two Midwestern wastewater treatment plants, making sure to get samples from every step of treatment. The main purpose was to see if the MRSA was still present in the water to be used for irrigation.

“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. 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,” Amy R. Sapkota, assistant professor in the Maryland Institute for Applied Environmental Health and research study leader, said in a press release. “This was the first study to investigate U.S. wastewater as a potential environmental reservoir of MRSA.”

Sapkota and her colleagues’ findings were staggering.

MRSA was found in all four wastewater treatment plants, along with another pathogen methicillin-susceptible Staphylococcus aureus (MSSA). Of all the raw sewage, prior to any treatment, 83 present contained MRSA. The good news is this decreased at each stage of treatment. Water leaving three of the four plants, after chlorination (a common step in water treatment) contained no MRSA.

However,  treated water leaving one of the plants that doesn’t use chlorination, still contained MRSA.

Of  the MRSA strains identified at the plants, 93 percent were resistant to two or more classes of antibiotics. These included antibiotics that the FDA approved for treating the infection. The authors concluded that although the treatment plants that use chlorination remove the MRSA by the time the water is reclaimed, they may select for higher antibiotic resistance.

“Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater,” Rachel Rosenberg Goldstein, environmental health doctoral student in the School of Public Health and the study’s first author, said in a press release. “Because of increasing use of reclaimed wastewater, further research is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater.”


2 Responses to “MRSA found in U.S. wastewater treatment plants, study shows”

  1. Soumyadeep B November 6, 2012 at 6:42 pm #

    Read the Review of The Rise of Superbug MRSA in USA at :


  1. Scientists one step closer to deafeating ‘Superbug’ MRSA, study shows « Layman's Terms Media - February 5, 2013

    […] few medicines available to treat the infections caused by MRSA, scientists from Harvard’s Wyss Institute for Biologically Inspired Engineering and Boston […]

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