The Prevalence of tet(A) and tet(M) Tetracycline Resistance Genes in Municipal Wastewater

Antibiotic resistance is a widespread problem that poses one of the greatest risks to public health around the world. The main cause of antibiotic resistance is the overuse of antibiotics in the human and veterinary medicine and in agriculture. Drugs are released into the environment with treated wastewater, and they can act as stressors that increase the prevalence of antibiotic resistance genes (ARGs). Wastewater treatment plants (WWTPs) are not equipped with appropriate technologies for eliminating the genetic material from the treated wastewater. In this study, the prevalence of tet(A) and tet(M) genes encoding resistance to tetracycline antibiotics was investigated in the samples of municipal wastewater and sewage sludge collected from two WWTPs and in the water samples collected from rivers which receive the treated wastewater. The samples were collected in two seasons of the year (summer and fall). The presence of ARGs was confirmed by PCR. The study revealed that ARGs were not effectively removed from wastewater by the WWTP in the Region of Silesia. Seasonal variations in the occurrence of the analyzed genes were not observed in the samples collected from the above-mentioned plant. Tetracycline resistance genes were detected in all samples of river water. The tet(A) gene was not removed from the treated wastewater in the WWTP in the Region of Warmia and Mazury, whereas the tet(M) gene was detected on a seasonal basis. The tet(M) gene was not detected in the samples of river water collected upstream and downstream from the WWTP. The study demonstrated that the existing WWTPs lack the means to eliminate ARGs. The wastewater treatment systems have to be modified to effectively remove ARGs from the treated wastewater.