Abstract
Wastewater treatment plants (WWTPs) represent all known types of antibiotic resistance mechanisms and are considered as the critical points for the spread of antibiotic resistance genes (ARGs). The purpose of this study is to investigate the removal of a Class 1 integrase gene (intI1) and a selected set of ARGs (blaTEM, ermF, mecA, and tetA) at two conventional WWTPs by using chlorination in Louisiana, USA. We collected 69 wastewater samples (23 each from influent, secondary effluent, and final effluent) and determined the concentrations of ARGs by using quantitative polymerase chain reaction. All tested ARGs, except for mecA, were detected in 83–96% and 30–65% of influent and final effluent samples, respectively. Although the ARGs underwent approximately 3-log10 reduction, two WWTPs on an average still released 3.3 ± 1.7 log10 copies/mL of total ARGs studied in the effluents. Chlorination was found to be critical in the significant reduction of total ARGs (p < 0.05). Correlation analysis and the ability of intI1 to persist through the treatment processes recommend the use of intI1 as a marker of ARGs in effluents to monitor the spread of antibiotic resistance in effluents. Our study suggests that conventional WWTPs using chlorination do not favor the proliferation of antibiotic resistance bacteria and ARGs during wastewater treatment.
Highlights
Despite the presence of bacteria that harbor antibiotic resistance genes (ARGs) in a pristine environment [1], studies have reported that an increase in ARGs is related to anthropogenic activities, such as discharge of feces in sewage and untreated wastewater [2,3]
Total bacterial 16S rRNA was detected in all the samples, whereas methicillin resistance gene (mecA) was not detected in any of the wastewater samples
This study demonstrated the ability of Wastewater treatment plants (WWTPs) to significantly reduce ARGs and intI1 in wastewater
Summary
Despite the presence of bacteria that harbor antibiotic resistance genes (ARGs) in a pristine environment [1], studies have reported that an increase in ARGs is related to anthropogenic activities, such as discharge of feces in sewage and untreated wastewater [2,3]. The spread of such bacteria and ARGs has led to antibiotic resistance becoming a major public health issue [4]. WWTPs can provide environmental conditions potentially favoring the persistence of ARGs and are considered “hotspots” [5] or “critical points” [6] for the spread of ARGs in the environment.
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