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Aerobic digestion reduces the quantity of antibiotic resistance genes in residual municipal wastewater solids.

Burch TR, Sadowsky MJ, Lapara TM - Front Microbiol (2013)

Bottom Line: Numerous initiatives have been undertaken to circumvent the problem of antibiotic resistance, including the development of new antibiotics, the use of narrow spectrum antibiotics, and the reduction of inappropriate antibiotic use.During this time, the quantities of tet(A), tet(W), and erm(B) decreased by more than 90%.In contrast, intI1 did not decrease, and tet(X) increased in quantity by 5-fold.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil Engineering, University of Minnesota Minneapolis, MN, USA.

ABSTRACT
Numerous initiatives have been undertaken to circumvent the problem of antibiotic resistance, including the development of new antibiotics, the use of narrow spectrum antibiotics, and the reduction of inappropriate antibiotic use. We propose an alternative but complimentary approach to reduce antibiotic resistant bacteria (ARB) by implementing more stringent technologies for treating municipal wastewater, which is known to contain large quantities of ARB and antibiotic resistance genes (ARGs). In this study, we investigated the ability of conventional aerobic digestion to reduce the quantity of ARGs in untreated wastewater solids. A bench-scale aerobic digester was fed untreated wastewater solids collected from a full-scale municipal wastewater treatment facility. The reactor was operated under semi-continuous flow conditions for more than 200 days at a residence time of approximately 40 days. During this time, the quantities of tet(A), tet(W), and erm(B) decreased by more than 90%. In contrast, intI1 did not decrease, and tet(X) increased in quantity by 5-fold. Following operation in semi-continuous flow mode, the aerobic digester was converted to batch mode to determine the first-order decay coefficients, with half-lives ranging from as short as 2.8 days for tet(W) to as long as 6.3 days for intI1. These results demonstrated that aerobic digestion can be used to reduce the quantity of ARGs in untreated wastewater solids, but that rates can vary substantially depending on the reactor design (i.e., batch vs. continuous-flow) and the specific ARG.

No MeSH data available.


Related in: MedlinePlus

The quantities of 16S rRNA genes and fecal indicator bacteria as measured by 16S rRNA genes of all Bacteroides spp. in untreated (closed circles) and treated (open circles) residual solids. Values are the arithmetic mean of triplicate samples; error bars represent one standard deviation. The concentrations of human-specific Bacteroides spp. were approximately 5 × 108 gene copies mL−1 in untreated samples, but were below the detection limit (1×108 gene copies mL−1) in treated samples.
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Figure 1: The quantities of 16S rRNA genes and fecal indicator bacteria as measured by 16S rRNA genes of all Bacteroides spp. in untreated (closed circles) and treated (open circles) residual solids. Values are the arithmetic mean of triplicate samples; error bars represent one standard deviation. The concentrations of human-specific Bacteroides spp. were approximately 5 × 108 gene copies mL−1 in untreated samples, but were below the detection limit (1×108 gene copies mL−1) in treated samples.

Mentions: The aerobic digester eliminated a substantial fraction of bacterial biomass and fecal indicator bacteria (FIB) as measured by qPCR targeting the 16S rRNA gene and 16S rRNA genes specific for all Bacteroides spp. and for human-specific Bacteroides spp. (Figure 1). The concentrations of 16S rRNA genes were 77% lower in treated samples compared to the untreated samples. This indicates net destruction of total bacterial biomass in the digester, consistent with the total and volatile solids removal. Significant removal was observed for both types of FIB. The concentrations of all Bacteroides spp. were 99.9% lower in treated samples compared to untreated samples. Similarly, the concentrations of human-specific Bacteroides spp. were approximately 5×108 gene copies mL−1 in untreated samples, but were below the detection limit (1×108 gene copies mL−1) in treated samples.


Aerobic digestion reduces the quantity of antibiotic resistance genes in residual municipal wastewater solids.

Burch TR, Sadowsky MJ, Lapara TM - Front Microbiol (2013)

The quantities of 16S rRNA genes and fecal indicator bacteria as measured by 16S rRNA genes of all Bacteroides spp. in untreated (closed circles) and treated (open circles) residual solids. Values are the arithmetic mean of triplicate samples; error bars represent one standard deviation. The concentrations of human-specific Bacteroides spp. were approximately 5 × 108 gene copies mL−1 in untreated samples, but were below the detection limit (1×108 gene copies mL−1) in treated samples.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569665&req=5

Figure 1: The quantities of 16S rRNA genes and fecal indicator bacteria as measured by 16S rRNA genes of all Bacteroides spp. in untreated (closed circles) and treated (open circles) residual solids. Values are the arithmetic mean of triplicate samples; error bars represent one standard deviation. The concentrations of human-specific Bacteroides spp. were approximately 5 × 108 gene copies mL−1 in untreated samples, but were below the detection limit (1×108 gene copies mL−1) in treated samples.
Mentions: The aerobic digester eliminated a substantial fraction of bacterial biomass and fecal indicator bacteria (FIB) as measured by qPCR targeting the 16S rRNA gene and 16S rRNA genes specific for all Bacteroides spp. and for human-specific Bacteroides spp. (Figure 1). The concentrations of 16S rRNA genes were 77% lower in treated samples compared to the untreated samples. This indicates net destruction of total bacterial biomass in the digester, consistent with the total and volatile solids removal. Significant removal was observed for both types of FIB. The concentrations of all Bacteroides spp. were 99.9% lower in treated samples compared to untreated samples. Similarly, the concentrations of human-specific Bacteroides spp. were approximately 5×108 gene copies mL−1 in untreated samples, but were below the detection limit (1×108 gene copies mL−1) in treated samples.

Bottom Line: Numerous initiatives have been undertaken to circumvent the problem of antibiotic resistance, including the development of new antibiotics, the use of narrow spectrum antibiotics, and the reduction of inappropriate antibiotic use.During this time, the quantities of tet(A), tet(W), and erm(B) decreased by more than 90%.In contrast, intI1 did not decrease, and tet(X) increased in quantity by 5-fold.

View Article: PubMed Central - PubMed

Affiliation: Department of Civil Engineering, University of Minnesota Minneapolis, MN, USA.

ABSTRACT
Numerous initiatives have been undertaken to circumvent the problem of antibiotic resistance, including the development of new antibiotics, the use of narrow spectrum antibiotics, and the reduction of inappropriate antibiotic use. We propose an alternative but complimentary approach to reduce antibiotic resistant bacteria (ARB) by implementing more stringent technologies for treating municipal wastewater, which is known to contain large quantities of ARB and antibiotic resistance genes (ARGs). In this study, we investigated the ability of conventional aerobic digestion to reduce the quantity of ARGs in untreated wastewater solids. A bench-scale aerobic digester was fed untreated wastewater solids collected from a full-scale municipal wastewater treatment facility. The reactor was operated under semi-continuous flow conditions for more than 200 days at a residence time of approximately 40 days. During this time, the quantities of tet(A), tet(W), and erm(B) decreased by more than 90%. In contrast, intI1 did not decrease, and tet(X) increased in quantity by 5-fold. Following operation in semi-continuous flow mode, the aerobic digester was converted to batch mode to determine the first-order decay coefficients, with half-lives ranging from as short as 2.8 days for tet(W) to as long as 6.3 days for intI1. These results demonstrated that aerobic digestion can be used to reduce the quantity of ARGs in untreated wastewater solids, but that rates can vary substantially depending on the reactor design (i.e., batch vs. continuous-flow) and the specific ARG.

No MeSH data available.


Related in: MedlinePlus