Superbug Lurks in US Water Treatment Facilities

MRSA (methicillin-resistant Staphylococcus aureus) 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, the potential environmental sources of MRSA or how people in the community come in contact with this microorganism are not well understood.  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 (WWTPs) in Sweden. Amy R. Sapkota, from the Maryland Institute for Applied Environmental Health (Maryland, USA), and colleagues collected wastewater samples throughout the treatment process at four US WWTPs, each of discharges treated effluent as “reclaimed wastewater” for use in landscaping spray irrigation activities. The researchers found that MRSA, as well as a related pathogen, methicillin-susceptible Staphylococcus aureus (MSSA),were present at all four WWTPs, with MRSA in half of all samples and MSSA in 55%.MRSA was present in 83% of the influent– the raw sewage–at all plants, but the percentage of MRSA- and MSSA-positive samples decreased as treatment progressed.  Warning that: “Our findings raise potential public health concerns for wastewater treatment plant workers and individuals exposed to reclaimed wastewater,” the study authors urge that: “Because of increasing use of reclaimed wastewater, further study is needed to evaluate the risk of exposure to antibiotic-resistant bacteria in treated wastewater.”