Methicillin-resistant Staphylococcus aureus (MRSA) in municipal wastewater: an uncharted threat?

Authors

  • S. Börjesson,

    1.  Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
    2.  Department of Animal Health and Antimicrobial Strategies, The National Veterinary Institute (SVA), Uppsala, Sweden
    3.  Department of Clinical Microbiology, County Hospital Ryhov, Jönköping, Sweden
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  • A. Matussek,

    1.  Department of Clinical Microbiology, County Hospital Ryhov, Jönköping, Sweden
    2.  Laboratory Services, Unilabs, Göteborg, Sweden
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  • S. Melin,

    1.  Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
    2.  Department of Clinical Microbiology, County Hospital Ryhov, Jönköping, Sweden
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  • S. Löfgren,

    1.  Department of Clinical Microbiology, County Hospital Ryhov, Jönköping, Sweden
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  • P.E. Lindgren

    1.  Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden
    2.  Department of Clinical Microbiology, County Hospital Ryhov, Jönköping, Sweden
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Andreas Matussek, Medical Director, Region Lab North, Unilabs, Kilsgatan 4, SE-405 22 Gothenburg, Sweden. E-mail: andreas.matussek@unilabs.com

Abstract

Aims:  (i) To cultivate methicillin-resistant Staphylococcus aureus (MRSA) from a full-scale wastewater treatment plant (WWTP), (ii) To characterize the indigenous MRSA-flora, (iii) To investigate how the treatment process affects clonal distribution and (iv) To examine the genetic relation between MRSA from wastewater and clinical MRSA.

Methods:  Wastewater samples were collected during 2 months at four key sites in the WWTP. MRSA isolates were characterized using spa typing, antibiograms, SSCmec typing and detection of Panton–Valentine leukocidin (PVL).

Conclusions:  MRSA could be isolated on all sampling occasions, but only from inlet and activated sludge. The number of isolates and diversity of MRSA were reduced by the treatment process, but there are indications that the process was selected for strains with more extensive antibiotic resistance and PVL+ strains. The wastewater MRSA-flora had a close genetic relationship to clinical isolates, most likely reflecting carriage in the community.

Significance and Impact of the Study:  This study shows that MRSA survives in wastewater and that the WWTP may be a potential reservoir for MRSA.

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