Comparison of the elimination effectiveness of tetracycline and AmpC β-lactamase resistance genes in a municipal wastewater treatment plant using four parallel processes

Abstract

Municipal wastewater treatment plants (mWWTPs), considered reservoirs of antibiotic resistance genes (ARGs), are selected to compare the contributions of technology and process to ARG removal. Fifteen ARGs (tetA, tetB, tetC, tetE, tetG, tetL, tetM, tetO, tetQ, tetS, tetX, MOX, CIT, EBC, and FOX) and two integron genes (intI1, intI2) were tracked and detected in wastewater samples from a large-scale mWWTP with four parallel processes, including three biological technologies of AAO (anaerobic-anoxic-oxic), AB (adsorption-biodegradation), and UNITANK, two different disinfection technologies, and two primary sedimentation steps. The results showed that ARGs were widely detected, among which tetA and tetM had the highest detection rate at 100%. AAO was the most effective process in removing ARGs, followed by the AB and UNITANK processes, where the separation step was critical: 37.5% AmpC β-lactamase genes were reduced by the secondary clarifier. UV disinfection was more efficient than chlorination disinfection by 47.0% in ARG removal. Both disinfection and primary sedimentation processes could effectively remove integrons, and the swirling flow grit chamber was a more effective primary settling facility in total ARG removal than the aerated grit chamber. The tet genes and AmpC β-lactamase genes were significantly correlated with the water quality indexes of BOD 5 , COD Cr , SS, TP, TOC, pH and NH 4 +-N (p < 0.05). In addition, the correlation between efflux pump genes and AmpC β-lactamase genes was strongly significant (r 2 = 0.717, p < 0.01). This study provides a more powerful guide for selecting and designing treatment processes in mWWTPs with additional consideration of ARG removal.

Design and validation of primer sets for the detection and quantification of antibiotic resistance genes in environmental samples by quantitative PCR

“…The low relative abundances of of aadB, ampC, bla SHV , bla TEM , dfrA1, qnrS, and tetA(A) genes suggests that these ARGs are not the dominant resistance mechanisms in the bacterial communities here analyzed. Similarly low relative abundances of these genes have been described in activated sludge from different WWTPs, anaerobic digestate, compost, riverine sediments, and agricultural soil samples for the aadB [43,49], ampC [25,50,51], bla SHV [25,52], bla TEM [2,12,25,[53][54][55][56], dfrA1 [6, 53,54,56,57], qnrS [59,60], and tetA(A) genes [51,53,54,57]. However, although these ARGs were detected in low relative abundances, their common occurrence implies a loss of the therapeutic effects of some of the most employed antibiotics compounds, resulting in treatment failures in both developed and developing countries and could be important agents in the exacerbation of antibiotic resistance emergence [61].…”

Design and Validation of Primer Sets for the Detection and Quantification of Antibiotic Resistance Genes in Environmental Samples by Quantitative PCR

“…The low relative abundances of aadB , ampC , bla SHV , bla TEM , dfrA 1, qnrS , and tetA (A) genes suggests that these ARGs are not the dominant resistance mechanisms in the bacterial communities here analyzed. Similarly, low relative abundances of these genes have been described in activated sludge from different WWTPs, anaerobic digestate, compost, riverine sediments, and agricultural soil samples for the aadB [ 37 , 40 ], ampC [ 14 , 41 ], bla SHV [ 14 , 42 ], bla TEM [ 6 , 14 , 43 ], dfrA 1 [ 3 , 43 , 44 ], qnrS [ 2 , 45 ], and tetA (A) genes [ 41 , 44 ]. However, although these ARGs were detected in low relative abundances, their common occurrence implies a loss of the therapeutic effects of some of the most employed antibiotics, resulting in treatment failures in both developed and developing countries, and could be important agents in the exacerbation of antibiotic resistance emergence.…”

Unseen Weapons: Bacterial Extracellular Vesicles and the Spread of Antibiotic Resistance in Aquatic Environments

“…The floR gene confers resistance to florfenicol, which is a broad-spectrum antibiotic used in veterinary medicine, particularly in the treatment of bacterial infections in animals [ 77 ]. The presence of the floR gene in bacteria can lead to resistance against florfenicol, limiting the effectiveness of this antibiotic in treating infections caused by such bacteria.…”