MRSA Discovered in U.S. Wastewater Treatment Plants

Researchers, led by scientists from the University of Maryland School of Public Health, confirmed that methicillin-resistant Staphylococcus aureus, or MRSA, exists in the U.S. wastewater treatment plants.

Staphyloccoccus aureus, or staph, is a bacterium responsible for infections contracted in hospital settings that are noted for being difficult to treat and potentially fatal. The bacteria can be present without causing an active infection.

Beginning in the late 1990s, MRSA has also been infecting otherwise healthy people in community settings, which is known as community-associated MRSA.

Amy R. Sapkota, assistant professor in the Maryland Institute for Applied Environmental Health, who headed the study, explains:

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. […] This was the first study to investigate U.S. wastewater as a potential environmental reservoir of MRSA.

Those individuals who are infected with MRSA can shed bacterium from their noses and skin as well as through their feces. This means bacteria can likely be found in wastewater treatment plants.

Prior to this latest research by scientists from the University of Maryland School of Public Health and University of Nebraska Medical Center, Swedish researchers identified the presence of MRSA in wastewater treatment plants in Sweden.

The Staphyloccoccus aureus was first discovered in the 1880s, according to The National Institute of Allergy and Infectious Diseases. The infection was associated with “painful skin and soft tissue conditions such as boils, scalded-skin syndrome, and impetigo,” although it can also result in bacterial pneumonia or enter the bloodstream, which can prove fatal.

The advent of widely available antibiotics, including penicillin, in the 1940s helped treat staph infections. Antibiotics’ continued mis- and overuse advanced this bacteria’s evolution into a drug-resistant microbe. Initially, staph infections became resistant to penicillin, then methicillin.

Methicillin-resistant Staphylococcus aureus was initially identified in 1961 by British researchers. The first case in the United States was reported in 1968.

Different strains of the staph bacteria are now immune to once-effective drug therapies, including a range of penicillin-like antibiotics and vancomycin. Although vancomycin-resistant strains of staph are still rare, their emergence concerns health care professionals.

The American scientists collected samples from four different water treatment plants, selected because treated effluent or recycled water from them is used for irrigation.

The researchers reported finding MRSA and a related pathogen — methicillin-susceptible Staphylococcus aureus, or MSSA — at all four facilities. MRSA was reportedly present in 83% of the raw sewage at all plants. They reported that “the percentage of MRSA- and MSSA-positive samples decreased as treatment progressed. Only one WWTP 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.”

They concluded:

Our findings raise potential public health concerns for waste­water treatment plant workers and individuals exposed to reclaimed waste­water. Because of increasing use of reclaimed waste­water, further study is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated waste­water.

The researchers published their findings in the November 2012 issue of Environmental Health Perspectives.


Article originally published