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APHA project on the impact of AD treatment plants on reducing AMR organisms

The Animal and Plant Health Agency is working on a study of the effect of livestock industry biosecurity and hygiene measures on the occurrence and control of antimicrobial resistance. In order to develop the study, the APHA is looking for AD plants to provide sample to be analysed.

 

Background

Farm waste may contain a wide variety of antimicrobial resistant (AMR) bacteria, resistance genes and mobile genetic elements. Reducing AMR bacteria in manure is highly dependent on treatment parameters and on the residues and bacteria present.

The main waste management options employed worldwide and in GB are the storage of manure, composting and anaerobic digestion (AD). Different treatments have different impacts on AMR bacteria and antimicrobial resistance genes (ARGs). The presence of ARG carrying bacteria in the waste, which have survived treatment conditions, is reported to be a risk factor for these genes to be transferred to the environmental or to pathogenic bacteria after the spreading of treated waste.

The aim of the project is to assess the effect of different waste management treatments to minimise the presence of AMR bacteria (and ARGs) in farm waste following the treatment.

 

Approach and methodology

Up to twenty animal waste treatment plants covering different technologies will be visited. There are resources to cover 20 sampling visits (10 visits this financial year 2022/23 and 10 visits next financial year 2023/24), focusing on farm waste from dairy cattle and pig farms.

The types of plants to investigate have been identified through a review of the industry in the UK and by a literature review of the processes. Seven types of sites have been short listed for sampling:

  1. Mesophilic (35–42°C) Anaerobic Digester with a continuous flow of input material (e.g. Complete Mix Digester reactor)
  2. Mesophilic Anaerobic Digester that processes the material in batches (e.g. Anaerobic Sequence Batch Reactor)
  3. Plant with a pasteurization step before AD
  4. Site with covered slurry lagoons or tanks (passive anaerobic digestion)
  5. Site with uncovered lagoons used for storage (of slurry or of the liquid fraction after solid-liquid separation)
  6. Site that treats raw slurry through acidification.
  7. Site that performs composting (on raw manure or on the solid portion obtained after solid-liquid separation) before spreading

 

The sites will be selected in coordination with the Environmental Agency on their importance to waste treatment in the UK and practicality of recruitment and sampling of these plants.

Samples will be collected from waste before and after treatment to assess the effect on antimicrobial resistant bacteria and genes.

Key indicator organisms will be targeted (e.g. AMR E. coli) and the proportion of the bacterial population that is resistant to key antimicrobials will be quantified before and after treatment. Sensitive conventional microbiology will be supplemented by targeted use of whole genome sequencing and metagenomics.

 

What can you do?

AD operators who are interested to join the study by providing samples or opening their sites to APHA for samples collection can contact Charlotte MARCEL at ADBA to gather all the information to provide to APHA. Please specify the type of site that your AD plant is, from the 7 types plants list mentioned hereinabove.

charlotte.marcel@adbioresources.org 

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