Proliferation of Multidrug-Resistant New Delhi Metallo-β-lactamase Genes in Municipal Wastewater Treatment Plants in Northern China

Abstract

The New Delhi metallo-β-lactamase (NDM-1) increases bacterial resistance to a broad range of antibiotics, and bacteria that produce it can cause infections that are very difficult to treat, thus posing great risks to human health. This paper addresses the occurrence of NDM-1 genes through different processes in wastewater treatment plants (WWTPs). NDM-1 genes prevailed through several treatment units (including disinfection by chlorination) in two WWTPs in northern China. Significant NDM-1 gene levels were present in the effluent discharged from both WWTPs (from 1316 ± 232 to 1431 ± 247 copies/mL, representing from 4.4 to 93.2%, respectively, of influent levels). NDM-1 genes were present at much higher concentrations in dewatered waste sludge that is applied to soils [(4.06 ± 0.98) × 107 to (6.21 ± 2.23) × 107 copies/g of dry weight], raising the possibility of propagation to indigenous bacteria. This concern was validated by a conjugation experiment with Haihe River sediment not harboring NDM-1 genes at detectable levels, where an NDM-1-positive Achromobacter sp. isolated from a WWTP transferred the NDM-1 gene to an indigenous Comamonas sp. The discharge of NDM-1 genes in the effluent and dewatered waste sludge from WWTPs (even at rates higher than influent values) underscores the need to better understand and mitigate their proliferation and propagation from WWTPs.

Occurrences and Characterization of Antibiotic-Resistant Bacteria and Genetic Determinants of Hospital Wastewater in a Tropical Country

“…A survey of hospital wastewaters in Spain indicated levels of bla TEM , erm(B), qnrS, sul1, and tet(W) of between 10 5 and 10 6 gene copies/ml, which is slightly lower than the measured concentrations of ARGs in our study (12). In comparison to the domestic wastewaters in China, the levels of the 4 ␤-lactamase ARGs in our study (i.e., bla NDM , bla KPC , bla SHV , and bla CTX-M ) were 1 order of magnitude higher than those of the carbapenemase ARGs (i.e., bla NDM , bla KPC , bla OXA , and bla IMP ) detected in China (46,47). However, the concentrations of total 16S rRNA genes in our hospital wastewaters were slightly lower than those in the domestic wastewaters, which suggests a higher prevalence of these ARGs in hospital wastewaters.…”

Carbapenem-resistant bacteria in a secondary wastewater treatment plant

“…A significant positive correlation of CRBP with intestinal enterococci and total heterotrophic bacteria in the wastewater treatment plant (Table 2) suggests that the concentrations of CRBP through the plant were primarily attributable to the changes in total bacterial abundance rather than to efficiency of its removal. This observation is consistent with the report of a positive correlation of NDM-1 and 16S rRNA genes used as surrogates for multidrug resistant and total bacteria, respectively, in the secondary type of municipal wastewater treatment plant (Luo et al, 2014). A significant positive correlation of CRBP and suspended solids suggests that CRBP is removed from wastewater with the primary and excess secondary activated sludge, a process which needs future examination.…”

“…Hospital wastewater is recognised as a diffusion reservoir of New Delhi metallo-beta-lactamase-1 (NDM-1) producing bacteria (Zhang et al, 2013). Although the NDM-1 represents one of many mechanisms of carbapenem resistance, genes encoding NDM-1 were present in the domestic and industrial wastewater and each stage of the wastewater treatment process, including the chlorinated effluent (Luo et al, 2014). The finding of KPC-2-producing Gram-negative bacteria after the passage of hospital wastewater through the tertiary wastewater treatment plant (Chagas et al, 2011) suggests a resistance of CRBP to the process of chlorine disinfection.…”

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

“…An elevated level of ARGs has been observed in WWTP effluent after mixed-media filtration and hypochlorite disinfection (LaPara et al, 2011). The New Delhi metallo-β-lactamase (NDM-1) genetic element, which imparts resistance to a wide variety of antibiotics, has recently been found in WWTP effluent in China, and was able to be propagated to indigenous bacteria in the receiving environment (Luo et al, 2014). Given the environmental impacts and persistence of ARBs and ARGs, there is an urgent need to understand removal mechanisms and take steps towards formulation of effective removal strategies.…”