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Impact of untreated hospital effluents on dissemination of antibiotic resistance genes

Kayalı, Osman
Hospital wastewaters (HWWs) were reported to be hotspots for antibiotics and antibiotic-resistant bacteria. However, little is known about the impact of these effluents on the dissemination of antibiotic-resistance genes (ARGs). In this study, therefore, HWWs were monitored for 16S rRNA gene for overall bacterial genes and seven ARGs of aadA, tetA, cmlA, sul1, qnrS, ermB and blaCTX-M corresponding to commonly used antibiotics aminoglycosides, tetracyclines, amphenicols, sulfonamides, quinolones, macrolide-lincosamide-streptogramin group and β-lactams, respectively. Seasonally collected effluents of six different hospitals were analysed in terms of overall bacterial genes and seven ARGs by using quantitative polymerase chain reaction. Overall bacterial gene copy numbers were found to be the lowest with 103 copies/mL in winter, while the highest copy numbers with 105 copies/mL were observed in both summer and spring. All the hospitals tested displayed almost similar seasonal ARG copy number profile of aadA > tetA > cmlA ≈ sul1 > ermB ≈ qnrS > blaCTX-M. One-way analysis of variance elucidated that seasonal changes in ARG copy numbers were significant (p<0.05). The results indicated that untreated HWWs were hotspots for ARGs and required on-site treatment before discharging into public sewer.