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Updated: May 17, 2026
Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
Published on: May 8, 2013
Methicillin-resistant Staphylococcus aureus (MRSA) detected at four U.S. wastewater treatment plants
Rachel E Rosenberg Goldstein1, Shirley A Micallef, Shawn G Gibbs
1Maryland Institute for Applied Environmental Health, University of Maryland School of Public Health, College Park, Maryland 20742, USA.
Background:
The incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections is increasing in the United States, and it is possible that municipal wastewater could be a reservoir of this microorganism. To date, no U.S. studies have evaluated the occurrence of MRSA in wastewater.
Objective:
We examined the occurrence of MRSA and methicillin-susceptible S. aureus (MSSA) at U.S. wastewater treatment plants.
Methods:
We collected wastewater samples from two Mid-Atlantic and two Midwest wastewater treatment plants between October 2009 and October 2010. Samples were analyzed for MRSA and MSSA using membrane filtration. Isolates were confirmed using biochemical tests and PCR (polymerase chain reaction). Antimicrobial susceptibility testing was performed by Sensititre® microbroth dilution. Staphylococcal cassette chromosome mec (SCCmec) typing, Panton-Valentine leucocidin (PVL) screening, and pulsed field gel electrophoresis (PFGE) were performed to further characterize the strains. Data were analyzed by two-sample proportion tests and analysis of variance.
Results:
We detected MRSA (n = 240) and MSSA (n = 119) in 22 of 44 (50%) and 24 of 44 (55%) wastewater samples, respectively. The odds of samples being MRSA-positive decreased as treatment progressed: 10 of 12 (83%) influent samples were MRSA-positive, while only one of 12 (8%) effluent samples was MRSA-positive. Ninety-three percent and 29% of unique MRSA and MSSA isolates, respectively, were multidrug resistant. SCCmec types II and IV, the pvl gene, and USA types 100, 300, and 700 (PFGE strain types commonly found in the United States) were identified among the MRSA isolates.
Conclusions:
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.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) was detected in 50% of U.S. wastewater samples, decreasing significantly after treatment. This highlights potential public health risks for wastewater workers and those exposed to reclaimed water.
Area of Science:
- Environmental microbiology
- Public health
- Wastewater treatment
Background:
- Increasing incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections in the U.S.
- Potential role of municipal wastewater as a reservoir for MRSA
- Lack of prior U.S. studies on MRSA occurrence in wastewater
Purpose of the Study:
- To investigate the presence of MRSA and methicillin-susceptible S. aureus (MSSA) in U.S. wastewater treatment plants
- To assess the prevalence and characteristics of these bacteria in different stages of wastewater treatment
Main Methods:
- Collection of wastewater samples from four treatment plants over one year
- Analysis using membrane filtration, biochemical tests, and PCR
- Antimicrobial susceptibility testing, SCCmec typing, PVL screening, and PFGE for strain characterization
Main Results:
- MRSA detected in 50% and MSSA in 55% of samples
- MRSA prevalence decreased significantly from influent (83%) to effluent (8%)
- High rates of multidrug resistance observed in both MRSA (93%) and MSSA (29%) isolates
- Identification of common U.S. MRSA strains, including SCCmec types II and IV, and PVL gene
Conclusions:
- Wastewater treatment plants may harbor MRSA and MSSA
- Findings indicate potential public health concerns for wastewater workers and exposure to reclaimed water
- Further research is necessary to evaluate risks associated with antibiotic-resistant bacteria in treated wastewater
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