Abundance and Distribution of Tetracycline Resistance Genes and Mobile Elements in an Oxytetracycline Production Wastewater Treatment System

Abstract

We investigated the abundance and distribution of tetracycline resistance genes (tet genes) in an oxytetracycline (OTC) antibiotic production wastewater (APW) treatment system. Of sixteen tet genes and five mobile elements, nine tet genes (tet(A), tet(C), tet(G), tet(L), tet(M), tet(O), tet(Q), tet(W), and tet(X)) and two mobile elements (class 1 integron (intI1) and transposon Tn916/1545) were successfully quantified by real-time PCR. The relative abundance of tet genes in the effluent and activated sludge (1.2 × 10–4 to 1.3 × 100) of the APW treatment system were up to 2 orders of magnitude higher than those in the OTC fermentation residues (8.5 × 10–5 to 6.7 × 10–3) (P < 0.01), and 1–4 orders of magnitude higher than those in sewage and nonantibiotic production wastewater treatment systems (P < 0.01), showing that the discharge of abundant tet genes from the APW treatment system is worthy of attention. The three most abundant genes in the APW treatment system, tet(A), tet(C), and tet(G), exhibited significant positive correlations with intI1 (R 2 = 0.73, 0.95, and 0.83, respectively; P < 0.05), suggesting that intI1 may be involved in their proliferation. This is the first study showing that some measures may be required to control the discharge of antibiotic resistance genes from treated APW and activated sludge.

Impact of reclaimed water irrigation on antibiotic resistance in public parks, Beijing, China

“…1). On the one hand, factors, such as irrigation volume, frequency, and removal efficiency of antibiotics in WWTPs may lead to different concentrations of antibiotic residues in soils (Leung et al, 2012;Liu et al, 2012;. On the other hand, different antibiotic physicochemical property and structure could also influence the existence of antibiotics in environment.…”

“…In addition, there were no similar change patterns about the abundance of ARGs among different samples in the same park, which were collected from rhizosphere, non-rhizosphere, and wetland, respectively. Multiple factors could result in this phenomenon, such as irrigation volume, frequency, and the abundance of ARGs in reclaimed water as well as soil conditions (Auerbach et al, 2007;Gao et al, 2012b;Liu et al, 2012).…”

“…However, the conventional biological processes in WWTPs could not remove the antibiotics and resistant bacteria completely, which could be influenced by compound-specific properties and treatment processes in specific WWTPs, such as hydraulic retention time (HRT) and solid retention time (SRT) (Rizzo et al, 2013;Lindberg et al, 2005;Li and Zhang, 2010). Numerous studies have reported the occurrence of antibiotics in wastewater, sludge, and the removal efficiency of antibiotics by WWTPs (Leung et al, 2012;Liu et al, 2012;. For example, Gao et al (2012a) investigated the occurrence of antibiotics in eight sewage treatment plants in Beijing, China, and found that the removal efficiency of antibiotics varied significantly among the eight WWTPs, with average removal efficiency of fluoroquinolones, sulfonamides, and macrolides ranging from 48% to 72%, 39% to 64%, and À34% to 69%, respectively.…”

Effects of electron acceptors on removal of antibiotic resistant Escherichia coli, resistance genes and class 1 integrons under anaerobic conditions

“…Because the tubular BES was a mixed-culture system, the concentrations of target genes were normalized to that of 16S rRNA gene to minimize the variance in total bacterial population size and to gain insight into the possibility of horizontal gene transfer (Knapp et al, 2008;Liu et al, 2012). The serum bottles and two-chamber MEC contained only pure-culture E. coli, and thus the copy concentrations from those experiments were normalized to the sample volume (1 mL).…”

Response of activated sludge to the treatment of oxytetracycline production waste stream

“…Mother liquors (ML), which are the waste streams generated after filtration and antibiotic extraction during antibiotic production by fermentation (Environmental Protection Agency 2002; Liu et al 2012), are normally treated using biological processes after dilution (Li et al 2008;Ma et al 2009). Our previous study showed that activated sludge took two strategies to cope with the presence of residual antibiotics during antibiotic production wastewater treatment: preferential growth of functional bacteria possessing antibiotic resistance and preferential growth of fungi, neither of which were susceptible to antibiotics (Deng et al 2011;Li et al 2009Liu et al 2012).…”