Class 1 integronase gene and tetracycline resistance genes tetA and tetC in different water environments of Jiangsu Province, China

Abstract

Class 1 integronase gene (intI1) and tetracycline resistance genes (tetA and tetC) from various environmental sites in Jiangsu Province (China) were detected using qualitative PCR (polymerase chain reaction) and quantified with SYBR Green-based qRT-PCR (quantitative real-time PCR) in this study. Qualitative PCR assays demonstrated that intI1, tetA and tetC occurred in the water environments of Taihu Lake, the Nanjing section of the Yangtze River, a sewage treatment plant (STP) in Nanjing City, and two drinking water treating bioreactors. qRT-PCR results showed that abundance of intI1 in lake water and sediments was lower than the tet genes, for a given sample site and date (P < 0.05). On a volumetric basis, lake sediments contained higher concentrations of the three genes by four to five orders of magnitude than water samples, and lake water and sediments sampled in April contained fewer copies of all the genes than the samples collected in June and August (P < 0.05). The levels of intI1, tetA and tetC in the Yangtze River water increased significantly after the river flowed through Nanjing City (P < 0.05). 94.1% integron, 97.2% tetA and 98.3% tetC were removed by the activated sludge process in the STP, and more than 80% of each gene was removed in both of the two biofilters in terms of relative concentration based on sample volume. However, on the basis of DNA mass, lower removals were obtained for both the activated sludge and biofiltration processes.

Quantitative and qualitative impact of hospital effluent on dissemination of the integron pool

“…Class 1 integrons were the most frequent integrons in all samples, and their concentrations in the WWTP influent and effluent were similar to those previously reported in such samples (Zhang et al, 2009a, b). The high normalized copy number of class 1 integrons in wastewater samples supports the view that human activities are a major source of class 1 integrons (Wright et al, 2008;Moura et al, 2010;Rosewarne et al, 2010).…”

“…Although more than 90% of integrons were eliminated, the normalized copy number of class 1 and class 2 integrons was not reduced, and around 10 16 integrons were released each day into environmental water ( Figure 5). It has previously been shown that activated sludge processes, which reduce total bacterial loads, do not specifically eliminate bacteria harboring integrons (Ferreira da Silva et al, 2007;Zhang et al, 2009a). Nevertheless, we found that the WWTP reduced the diversity of gene cassette arrays contained in the raw wastewater, underlining the effect of the biological treatment on the anthropogenic integron pool arriving at the WWTP.…”

“…However, most previous studies involved bacterial isolation, but culture-dependent methods reveal only about 0.1% to 15% of the overall bacterial diversity (Amann et al, 1995). Metagenomic studies have underlined the important role of integrons in environmental antibiotic-resistance dissemination via WWTPs (Zhang et al, 2009a;Moura et al, 2010;Gaze et al, 2011). WWTPs collect effluents from diverse sources, including hospitals, private households and factories.…”

Distribution of ten antibiotic resistance genes in E. coli isolates from swine manure, lagoon effluent and soil collected from a lagoon waste application field

“…Jindal et al (2006) found that <1% of isolates from lagoon samples had tetA and tetC genes. Using an activated sludge treatment, Zhang et al (2009) removed 97.7% and 98.3% of isolates with tetA and tetC genes, respectively. In a manure study, both tetA and tetC gene recovery were 4.32 log in composted manure and 8.4 log in untreated swine manure (Yu et al 2005).…”

Microbial community distribution and dominant bacterial species analysis in the bio-electrochemical system treating low concentration cefuroxime

“…The author found that a class 1 integron may locate on the resistance plasmid. Zhang et al concentrated on the detection and the distribution of the class 1 integronase gene in different water environments because mobile integrons are associated with ARG dissemination [40]. The authors considered that the microbes containing integrons may be inhibited by the effect of the external electric field, and the ARGs carried by the integrons may be missing.…”