Metagenomic Profiling of Antibiotic Resistance Genes and Mobile Genetic Elements in a Tannery Wastewater Treatment Plant

Abstract

Antibiotics are often used to prevent sickness and improve production in animal agriculture, and the residues in animal bodies may enter tannery wastewater during leather production. This study aimed to use Illumina high-throughput sequencing to investigate the occurrence, diversity and abundance of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in aerobic and anaerobic sludge of a full-scale tannery wastewater treatment plant (WWTP). Metagenomic analysis showed that Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria dominated in the WWTP, but the relative abundance of archaea in anaerobic sludge was higher than in aerobic sludge. Sequencing reads from aerobic and anaerobic sludge revealed differences in the abundance of functional genes between both microbial communities. Genes coding for antibiotic resistance were identified in both communities. BLAST analysis against Antibiotic Resistance Genes Database (ARDB) further revealed that aerobic and anaerobic sludge contained various ARGs with high abundance, among which sulfonamide resistance gene sul1 had the highest abundance, occupying over 20% of the total ARGs reads. Tetracycline resistance genes (tet) were highly rich in the anaerobic sludge, among which tet33 had the highest abundance, but was absent in aerobic sludge. Over 70 types of insertion sequences were detected in each sludge sample, and class 1 integrase genes were prevalent in the WWTP. The results highlighted prevalence of ARGs and MGEs in tannery WWTPs, which may deserve more public health concerns.

Fate of antibiotic resistant cultivable heterotrophic bacteria and antibiotic resistance genes in wastewater treatment processes

“…Phyla (Firmicutes, proteobacteria, Actinobacteria and Bacteroidetes) identified in this study (Tables 3 and S4) were also found dominated in the activated sludge of WWTPs (Wang et al, 2013b;Yang et al, 2014). It should be noted that Aeromonas (48.94%) were dominant in the influent, but Bacillus (51.06%) were dominant in the effluent samples.…”

“…Morozzi et al (1988) found that, during aerobic treatment of urban sewage, there was a tendency for the percentage of ARB to increase. A recent report showed that aerobic and anaerobic sludge differed with respect to the abundance of different types of ARGs and the bacterial community structure and composition (Wang et al, 2013b). However, the detection frequency of ARGs decreased generally in cultivable heterotroph in the effluent, as compared to the influent (Tables S5 and S6).…”

“…A recent report showed that there is a difference in the bacterial community structure and composition between aerobic and anaerobic sludge (Wang et al, 2013b). Activated sludge usually contains uncultivable bacteria that are difficult to study by traditional molecular methods, and 16S rRNA gene sequences from many bacteria cannot even be assigned to taxonomic groups at the phylum or class levels .…”

“…However, minimal is known about the characteristics and species of antibiotic-resistant heterotrophic bacteria, which dominate in activated sludge (Reinthaler et al, 2003;Ferreira da Silva et al, 2007). Since most of the heterotrophic bacteria are uncultivable (Yang et al, 2014), qPCR methods are generally employed to investigate the ARGs at the samples level, including in samples from anaerobic and aerobic environment (Ma et al, 2011;Wang et al, 2013b) and WWTP sludge (Yang et al, 2014). However, the alterations in ARG concentrations under different bio-treatment processes remain unclear.…”

Integrons: Past, Present, and Future

“…Resistance genes and integrons are present in floc and sewage sludge (186,187), and despite the growing use of methods to remove such genes during wastewater treatment (188)(189)(190)(191), considerable quantities are released in reclaimed water (192) or directly into rivers (193,194), where they eventually make their way to estuaries and the ocean (171,195,196). Resistance genes and integrons are also disseminated in effluent from hospitals and in wastewater from tanneries (197,198). Further, the use of animal wastes as manure introduces resistance genes and integrons into agricultural soils (199)(200)(201)(202).…”