Saturday, November 3, 2012
Superbug Hideout: Finding MRSA in U.S.Wastewater Treatment Plants
For many years, the “superbug” methicillin-resistant Staphylococcus aureus (MRSA) was confined to hospital patients, but since the 1990s it has been infecting otherwise healthy people in settings such as schools and locker rooms. Researchers now report the discovery of MRSA in U.S. wastewater treatment plants (WWTPs), identifying another possible environmental reservoir for the bacteria [EHP 120(11):1551–1558; Rosenberg Goldstein et al.]. People shed MRSA from their nostrils and skin and in their feces, which makes wastewater a likely vector for the bacteria. Previous research had identified MRSA in Swedish WWTPs, but no studies had been conducted on U.S. facilities.
The researchers collected wastewater samples throughout the treatment process at two mid-Atlantic and two Midwestern WWTPs. MRSA, as well as pathogenic methicillin-susceptible Staphylococcus aureus (MSSA), were present at all four WWTPs, with MRSA detected in 50% of all samples and MSSA detected in 55%. Genetic testing of the MRSA isolates revealed traits common among exceptionally virulent community-acquired strains circulating in the United States. Most MRSA isolates and 29% of MSSA isolates showed resistance to two or more classes of antibiotics, including several that the U.S. Food and Drug Administration has specifically approved for treating MRSA infections.