Assessment of the contribution of wastewater sources to the diversity of antibiotic resistance in wastewater treatment plants
Sigala, J. and Unc, A., New Mexico State University, USA
(free)
Municipal wastewater treatment plants daily treat wastewater generated from residential, industrial, hospital, and other sources. A growing concern worldwide is the prevalence of antibiotic resistant microorganisms in wastewater treatment plants that can potentially survive treatment and be released out in the environment as effluent or biosolids. Our research goal was to determine the contribution of antibiotic resistant microorganisms from various sources within a municipality. Wastewater samples were collected from ten locations, four before entering wastewater treatment plant (representing hospital, residential, university, and mixed residential/industrial sources) and six samples within the treatment plant at the inflow (mixed), primary clarifiers, trickling filters, aeration basin, secondary clarifiers, and after chlorination/de-chlorination tank prior to being released as treated effluent. All samples were cultured under antibiotic stress using four groups of antibiotics (cefaclor, ciprofloxacin, doxycycline, and erythromycin) two concentrations for each antibiotic, lowest concentration at a breakpoint common for enterobacteria and a high concentration above the maximum breakpoint for all bacteria as described by EUCAST (www.eucast.org). We performed PCR with rpoB primers and DGGE (denaturing gradient gel electrophoresis) on polyacrylamide gels. We compared the rpoB fingerprints (profile) from each sample. Silver-stained polyacrylamide gels were scanned and processed using BioNumerics software; Principal Component and cluster analyses were carried out in Minitab™ and Genstat™. Results show that our selective approach can distinguish among sources; typically, higher antibiotic concentrations were more useful in discriminating among different sample locations. Same DGGE fingerprints can also be used to infer the effectiveness of treatment options on the diversity of antibiotic resistant microorganisms.
