This study used 454 pyrosequencing, Illumina high-throughput sequencing and metagenomic analysis to investigate bacterial pathogens and their potential virulence in a sewage treatment plant (STP) applying both conventional and advanced treatment processes. Pyrosequencing and Illumina sequencing consistently demonstrated that Arcobacter genus occupied over 43.42% of total abundance of potential pathogens in the STP. At species level, potential pathogens Arcobacter butzleri, Aeromonas hydrophila and Klebsiella pneumonia dominated in raw sewage, which was also confirmed by quantitative real time PCR. Illumina sequencing also revealed prevalence of various types of pathogenicity islands and virulence proteins in the STP. Most of the potential pathogens and virulence factors were eliminated in the STP, and the removal efficiency mainly depended on oxidation ditch. Compared with sand filtration, magnetic resin seemed to have higher removals in most of the potential pathogens and virulence factors. However, presence of the residual A. butzleri in the final effluent still deserves more concerns. The findings indicate that sewage acts as an important source of environmental pathogens, but STPs can effectively control their spread in the environment. Joint use of the high-throughput sequencing technologies is considered a reliable method for deep and comprehensive overview of environmental bacterial virulence.
Crayfish, carp, and crab threaten the consumer’s health due to the enrichment of the toxic elements. The concentration of the toxic elements (As, Cr, Cd, and Pb) in these aquatics was less investigated simultaneously in situ. In this study, the toxic elements in these aquatics from the same site of Hanchuan, Hubei Province, China were measured by ICP-MS to assess the enrichment of the four toxic elements in them and the health risk to the consumer. The results showed that the concentrations of these elements in muscle were lower than those in hepatopancreas/ liver, except for Cr in crayfish. Furthermore, the concentrations of Cd in the hepatopancreas of crayfish and crab exceeded the standards of China and the European Union. Accordingly, the hepatopancreas of crayfish and crab are not recommended for consumption. The estimated daily intake of these elements in the muscle of crayfish, carp, and crab did not exceed the provisional tolerable daily intakes, the corresponding target hazard quotient (THQ), and the cancer risk (CR) values for As were lower than 1 and 1 × 10–6, respectively. However, the accumulated consumption of the muscle of the three freshwater catches could result in a significant increase in the total THQ value. The total ingestion of the muscle of these catches should be limited. Collectively, these findings may renew interest in food safety and the health risk to humans owing to the consumption of freshwater catches.
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