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

Hubeny Jakub, Buta Martyna, Zieliński Wiktor, Harnisz Monika, Korzeniewska Ewa, Nowrotek Monika, Płaza Grażyna

Journal of Ecological Engineering

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2019

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Vol. 20, nr 10

1--6

EN

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.

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The Occurrence of Integrase Genes in Different Stages of Wastewater Treatment

Buta Martyna, Hubeny Jakub, Zieliński Wiktor, Korzeniewska Ewa, Harnisz Monika, Nowrotek Monika, Płaza Grażyna

Journal of Ecological Engineering

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2019

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Vol. 20, nr 10

39--45

EN

The uncontrolled use of antibiotics and the release of drug residuals into the environment contribute to antibiotic resistance and constitute a serious public health threat. The spread of antibiotic resistance can be attributed mainly to the huge amounts of bacteria harboring the antibiotic resistance genes (ARGs) which are released into the environment with the treated wastewater. The molecular mechanisms of antibiotic resistance, in which the mobile genetic elements (MGEs) such as plasmids, transposons, bacteriophages and integrons associated with the transfer of ARGs play the main role, should be broadly investigated to develop effective methods for addressing this problem. This study focused mainly on integrons which: (i) are the simple elements involved in the mobility of gene cassettes, (ii) have a common structure, (iii) can be associated with other MGEs, and (iv) are particularly efficient in trapping ARGs. The aim of the study was to estimate the efficiency of different stages of the wastewater treatment process in removing class 1, 2 and 3 integrase genes in two wastewater treatment plants (WWTPs) in Poland and to investigate the presence of these genes in river water upstream and downstream from the effluent discharge point. The presence of intI1, intI2 and intI3 genes was analysed by means of standard PCR with specific primers and a thermal cycling profiles. The samples of wastewater and sludge were collected from two WWTPs located in the Polish regions of (a) Warmia and Mazury, and (b) Silesia. The samples of river water were also collected upstream and downstream from the examined WWTPs. In the selected WWTPs, wastewater is treated through the activated sludge process with various modifications. The presence of intI1, intI2 and intI3 genes in different stages of wastewater treatment was characterized by a similar pattern. The results of this study indicate that WWTPs are not highly effective in removing the integrase genes from all three integron classes. The study revealed somewhat unexpected results, which indicate that the recently discontinued monitoring of the intI3 gene in the wastewater treatment process should be reinstated. The existing wastewater treatment systems should be improved and modified to effectively eliminate the integrase genes from wastewater and prevent contamination of the surface water.

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Prevalence of Beta Lactamases Genes in Sewage and Sludge Treated in Mechanical-Biological Wastewater Treatment Plants

Zieliński Wiktor, Buta Martyna, Hubeny Jakub, Korzeniewska Ewa, Harnisz Monika, Nowrotek Monika, Płaza Grażyna

Journal of Ecological Engineering

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2019

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Vol. 20, nr 9

80--86

EN

Wastewater treatment plants (WWTPs) are a very important link in the spread of antibiotic resistance genes to the environment and the formation of antibiotic-resistant microorganisms. The mechanical and biological methods of wastewater treatment in WWTPs do not completely remove the resistance genes from sewage. The genes responsible for extended-spectrum beta-lactamases (ESBLs) are very common in the family Enterobacteriaceae that colonize the human digestive tract and are abundant in wastewater. The aim of this study was to analyze the prevalence of genes encoding beta-lactamases in the wastewater and sludge samples collected from two WWTPs in the Polish regions of Warmia and Silesia and from the river water upstream and downstream from the WWTPs. The wastewater samples were passed through polycarbonate membrane filters, whereas the sludge samples were homogenized, and genomic DNA was extracted. The blaTEM, blaOXA and blaSHV genes were detected by means of standard PCR. The most prevalent gene was blaTEM which occurred in all samples, including the treated wastewater. The blaOXA gene was also frequently detected in all samples from the WWTP in Silesia. The blaSHV gene was least prevalent in the tested samples. These results indicate that wastewater is a hotspot for resistant bacteria. Beta-lactamase genes are not eliminated through the mechanical-biological wastewater treatment methods, and they can spread to other environments, thus increasing the pool of antibiotic resistance genes around the world and creating epidemiological risks.