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. 2023 Jan 24;11(2):308.
doi: 10.3390/microorganisms11020308.

Fate of Horizontal-Gene-Transfer Markers and Beta-Lactamase Genes during Thermophilic Composting of Human Excreta

Katharina A Werner  1 , Lara Feyen  1 , Tobias Hübner  2 , Nicolas Brüggemann  3 , Katharina Prost  3 , Elisabeth Grohmann  1
Affiliations

Fate of Horizontal-Gene-Transfer Markers and Beta-Lactamase Genes during Thermophilic Composting of Human Excreta

Katharina A Werner et al. Microorganisms. .

Abstract

Thermophilic composting is a suitable treatment for the recycling of organic wastes for agriculture. However, using human excreta as feedstock for composting raises concerns about antibiotic resistances. We analyzed samples from the start and end of a thermophilic composting trial of human excreta, together with green cuttings and straw, with and without biochar. Beta-lactamase genes blaCTX-M, blaIMP, and blaTEM conferring resistance to broad-spectrum beta-lactam antibiotics, as well as horizontal gene transfer marker genes, intI1 and korB, were quantified using qPCR. We found low concentrations of the beta-lactamase genes in all samples, with non-significant mean decreases in blaCTX-M and blaTEM copy numbers and a mean increase in blaIMP copy numbers. The decrease in both intI1 and korB genes from start to end of composting indicated that thermophilic composting can decrease the horizontal spread of resistance genes. Thus, thermophilic composting can be a suitable treatment for the recycling of human excreta.

Keywords: antibiotic resistance; compost; ecological sanitation; horizontal gene transfer; qPCR.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Copy numbers of beta-lactam ARGs blaIMP (A,B) and blaCTX-M (C,D), as well as blaTEM (E,F) as assessed by qPCR. Copy numbers were normalized to 16S rRNA gene copy numbers (left charts) and to 1 g compost (right charts). Bars represent the average of three individual qPCR measurements with standard deviation. Start samples, 14-days samples (only repetition 1) and end samples are depicted individually for the first (E1, E1-B) and second repetition of composting (E2, E2-B). End samples comprise replicates from front (end 1), middle (end 2) and back (end 3) of each compost pile. The p-values were calculated to compare start with end samples of composting for all four compost piles combined (average of the triplicate end samples, no differentiation of the treatments). None of the sample sets showed significance (p < 0.05). Therefore, they are indicated by “n.s.” (not significant).
Figure 2
Figure 2
Copy numbers of the class 1 integron-integrase gene intI1 (A,B) and IncP-1 marker gene korB (C,D) as assessed by qPCR. Copy numbers were normalized to 16S rRNA gene copy numbers (left charts) and to 1 g compost (right charts). Bars represent the average of three individual qPCR measurements with the standard deviation. Start samples, 14-days samples (only repetition 1) and end samples are depicted individually for the first (E1, E1-B) and second repetition of composting (E2, E2-B). End samples comprise replicates from the front (end 1), middle (end 2) and back (end 3) of each compost pile. Asterisks indicate the p-values obtained from Student’s t-test (* p < 0.05, ** p < 0.01) representing the statistical significance of the data. The p-values were calculated to compare start with end samples of composting for all four compost piles combined (average of the triplicate end samples, no differentiation of the treatments).
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References

    1. Rose C., Parker A., Jefferson B., Cartmell E. The characterization of feces and urine: A review of the literature to inform advanced treatment technology. Crit. Rev. Environ. Sci. Technol. 2015;45:1827–1879. doi: 10.1080/10643389.2014.1000761. - DOI - PMC - PubMed
    1. Ryals R., Bischak E., Porterfield K.K., Heisey S., Jeliazovski J., Kramer S., Pierre S. Toward zero hunger through coupled ecological sanitation-agriculture systems. Front. Sustain. Food Syst. 2021;5:716140. doi: 10.3389/fsufs.2021.716140. - DOI
    1. Bernal M.P., Alburquerque J.A., Moral R. Composting of animal manures and chemical criteria for compost maturity assessment. A review. Bioresour. Technol. 2009;100:5444–5453. doi: 10.1016/j.biortech.2008.11.027. - DOI - PubMed
    1. Ryckeboer J., Mergaert J., Vaes K., Klammer S., De Clercq D., Coosemans J., Insam H., Swings J. A survey of bacteria and fungi occurring during composting and self-heating processes. Ann. Microbiol. 2003;53:349–410.
    1. Godlewska P., Schmidt H.P., Ok Y.S., Oleszczuk P. Biochar for composting improvement and contaminants reduction. A review. Bioresour. Technol. 2017;246:193–202. doi: 10.1016/j.biortech.2017.07.095. - DOI - PubMed

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