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Researchers from the University of Maryland School of Public Health have found MRSA (methicillin-resistant Staphylococcus aureus) in wastewater treatment plants in 2 Mid-Atlantic and 2 Midwesterm facilities. The wastewater plants sparked the interest of researchers because they use treated and reclaimed wastewater for irrigation purposes.


Methicillin-resistant S aureus was found in the wastewater of half of all the samples analyzed and present in 83% of the raw sewage for all the treatment plants. Additionally, whereas MSSA (methicillin-susceptible S aureus) was in more than half the effluents, MRSA was present in the treated effluent, leaving only 1 facility. Wastewater treatment plants are thus a source of MRSA contamination and are able to contribute to the spread of the bacteria.


Also, 93% of the MRSA strains isolated from wastewater and 29% of the MSSA samples were resistant to 2 or more classes of antibiotics often used to treat these infections. On a more optimistic note, when wastewater treatment plants used chloride in their tertiary treatment process, both MRSA and MSSA were eliminated from effluent samples.


Methicillin-resistant S aureus spreads readily when people infected with MRSA shed the bacteria from their noses, skin, and through their feces. Unfortunately, this means wastewater treatment plants can serve as reservoirs for MRSA and MSSA. We need to understand that people working at wastewater treatment plants, those exposed to the reclaimed wastewater through irrigation or livestock management processes, and even those living nearby may be at much greater risk of developing the infection. Cautious evaluation of wastewater effluent prior to its use is advised. Nursing faculty, students, and practicing nurses can help to make the public and our wastewater treatment facilities more aware of this risk.


Source: Kessler R. Superbug hideout. Finding MRSA in U.S. wastewater treatment plants. Environmental Health Perspectives. November 1, 2012. Available at Accessed December 12, 2012.


Submitted by: Robin E. Pattillo, PhD, RN, CNL, News Editor at