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


CONCLUSIONS
This study shows that MRSA survives in wastewater and that the WWTP may be a potential reservoir for MRSA.
Börjesson
S
S
Department of Clinical and Experimental Medicine, Linköping University, Linköping, Sweden.
Matussek
A
A
Melin
S
S
Löfgren
S
S
Lindgren
P E
PE
D001426:Bacterial Proteins / Q000032:analysis; D016000:Cluster Analysis; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D008826:Microbial Sensitivity Tests; D012722:Sewage / Q000382:microbiology; D018508:Water Purification
D001426:Bacterial Proteins; D012722:Sewage