'Superbug' MRSA identified in U.S. wastewater treatment plants

Sponsored by

College Park, MD, Nov. 5, 2012 -- A team led by researchers at the University of Maryland School of Public Health has found that the superbug methicillin-resistant Staphylococcus aureus (MRSA) is prevalent at several U.S. wastewater treatment plants. MRSA is well known for causing difficult-to-treat and potentially fatal bacterial infections in hospital patients, but since the late 1990s it has also been infecting otherwise healthy people in community settings.

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

Because infected people can shed MRSA from their noses and skin and through their feces, wastewater treatment plants are a likely reservoir for the bacteria. Swedish researchers have previously identified the presence of MRSA in wastewater treatment plants in Sweden, and this new UMD-led study confirms the presence of MRSA in U.S. facilities. The study was published in the November issue of the Environmental Health Perspectives journal.

The research team, including University of Maryland School of Public Health and University of Nebraska Medical Center researchers, collected wastewater samples throughout the treatment process at two Mid-Atlantic and two Midwestern wastewater treatment plants. These plants were chosen, in part, because treated effluent discharged from these plants is reused as "reclaimed wastewater" in spray irrigation activities. The researchers were interested in whether MRSA remained in the effluent.

They found that MRSA, as well as a related pathogen, methicillin-susceptible Staphylococcus aureus (MSSA), were present at all four wastewater treatment plants, with MRSA in half of all samples and MSSA in 55 percent. MRSA was present in 83 percent of the influent -- the raw sewage -- at all plants, but the percentage of MRSA and MSSA-positive samples decreased as treatment progressed. Only one wastewater treatment plant had the bacteria in the treated water leaving the plant, and this was at a plant that does not regularly use chlorination, a tertiary step in wastewater treatment.

Ninety-three percent of the MRSA strains that were isolated from the wastewater and 29 percent of MSSA strains were resistant to two or more classes of antibiotics, including several that the U.S. Food and Drug Administration has specifically approved for treating MRSA infections. At two wastewater treatment plants, MRSA strains showed resistance to more antibiotics and greater prevalence of a gene associated with virulence at subsequent treatment stages, until tertiary chlorination treatment appeared to eliminate all MRSA. This suggests that while wastewater treatment plants effectively reduce MRSA and MSSA from influent to effluent, they may select for increased antibiotic resistance and virulence, particularly at those facilities that do not employ tertiary treatment (via chlorination).

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

###

Sponsored by

TODAY'S HEADLINES

Washington DOE approval granted to HaloSource for hybrid water treatment technology

HaloSource recently announced that it has received the Washington State Department of Ecology's General Use Level Designation for its BHR-P50 hybrid polymer used in conjunction with Chitosan Enhanced Sand Filtration system.

Case Study: Filter reduces flood-induced suspended solids in New Orleans heat exchangers

In New Orleans, fooding from Hurricane Katrina led to an in­crease in TSS, which caused fouling of the heat exchangers, resulting in a loss in efficiency and increase in maintenance costs. As such, Vortisand cross-flow microsand filter provided submicron filtration and high-quality water.

Tanks and Water Storage

US based manufacturer Fibrelite has seen a tremendous increase in inquiries for their lightweight composite access covers ...

Meeting Abu Dhabi's High Water Demands

Spurred on by a buoyant economy and population growth, the GCC countries are looking to invest $130 billion over the next decade to meet future demand and introduce new measures to achieve long-term sustainable water and energy supplies.

FOLLOW US ON SOCIAL MEDIA