Sewage treatment plant discharges impact the bacterial communities of streams, causing antibiotic resistance, Spanish researchers have found. Their study also showed that resistance was seen up to one kilometre downstream, presenting the possibility that antibiotic resistance in stream microbial biofilms could provide a biological indicator of anthropogenic pollution by active pharmaceutical compounds.
Researchers from the University of Girona and the University of the Basque Country studied four small streams. They used quantitative PCR analysis of biofilm samples taken upstream and downstream of wastewater treatment plant discharges. The samples were tested for genes giving resistance to the main antibiotic families – beta-lactams, fluoroquinolones, sulfonamides, and macrolides.
‘Our results showed that the WWTP effluents strongly modified the hydrology, physico-chemistry and biological characteristics of the receiving streams and favoured the persistence and spread of antibiotic resistance in microbial benthic communities,’ the researchers stated.
Low concentrations of antibiotic resistance genes were found upstream of the wastewater treatment plant discharges. A significant increase in the concentrations were found in the biofilms collected downstream of the discharges, and the researchers noted that the scale of the impact depended on the size of the discharge relative to the flow of the receiving water.
‘These findings suggest that WWTP discharges may favour the increase and spread of antibiotic resistance among streambed biofilms,’ the researchers stated. ‘The present study also showed that the presence of ARGs in biofilms was noticeable far downstream of the WWTP discharge (up to 1 km). It is therefore reasonable to assume that biofilms may represent an ideal setting for the acquisition and spread of antibiotic resistance determinants and thus be considered suitable biological indicators of anthropogenic pollution by active pharmaceutical compounds.’
‘Occurrence and persistence of antibiotic resistance genes in river biofilms after wastewater inputs in small rivers’, Proia L, von Schiller D, Sànchez-Melsió A, Sabater S, Borrego CM, Rodriguez-Mozaz S, Balcázar JL, Environmental Pollution, Vol 210, March 2016, pp121-128.
- Spain, municipal wastewater, pollution, antibiotic resistance