Dissipation of Antimicrobial Resistance Determinants in Composted and Stockpiled Beef Cattle Manure

Abstract

Windrow composting or stockpiling reduces the viability of pathogens and antimicrobial residues in manure. However, the impact of these manure management practices on the persistence of genes coding for antimicrobial resistance is less well known. In this study, manure from cattle administered 44 mg of chlortetracycline kg feed (dry wt. basis) (CTC), 44 mg of CTC and 44 mg of sulfamethazine kg feed (CTCSMZ), 11 mg of tylosin kg feed (TYL), and no antimicrobials (control) were composted or stockpiled over 102 d. Temperature remained ≥55°C for 35 d in compost and 2 d in stockpiles. Quantitative PCR was used to measure levels of 16S rRNA genes and tetracycline [(B), (C), (L), (M), (W)], erythromycin [(A), (B), (F), (X)], and sulfamethazine [(1), (2)] resistance determinants. After 102 d, 16S rRNA genes and all resistance determinants declined by 0.5 to 3 log copies per gram dry matter. Copies of 16S rRNA genes were affected ( < 0.05) by antimicrobials with the ranking of control > CTC = TYL > CTCSMZ. Compared with the control, antimicrobials did not increase the abundance of resistance genes in either composted or stockpiled manure, except (M) and (2) in CTCSMZ ( < 0.05). The decline in 16S rRNA genes and resistance determinants was higher ( < 0.05) in composted than in stockpiled manure. We conclude that composting may be more effective than stockpiling in reducing the introduction of antimicrobial resistance genes into the environment before land application of manure.

Effect of Co-Composting Cattle Manure with Construction and Demolition Waste on the Archaeal, Bacterial, and Fungal Microbiota, and on Antimicrobial Resistance Determinants

“…The Halocella genus, which was most relatively abundant in the middle sampling depth of the DDG compost, has only one species, Halocella cellulosilytica , a moderately halophilic, anaerobic cellulolytic bacterium [ 40 ]. The DDG compost did have significantly higher concentrations of ammonium (NH 4 + ), Mg 2+ , and total phosphorus, compared to the CON and CON C&D and inclusion of distillers’ grains in cattle diets typically increases the overall fibre content [ 11 ]. Thus, the increase in Halocella observed in the DDG compost may have resulted from differences in chemical composition compared to CON substrates, particularly the higher fibre content of the DDG treatment.…”

“…In addition, resistant bacteria and resistance determinants found in livestock feces can potentially increase in concentration if left untreated after excretion [ 8 , 37 ]. Composting of manure prior to application has been shown to be an effective method to reduce antimicrobial resistance determinants in cattle manure, compared to stockpiling [ 11 ]. Therefore it is important to study whether changes in the initial composition of compost affects the ability to reduce antimicrobial resistance.…”

Cropland Amendment with Beef Cattle Manure Minimally Affects Antimicrobial Resistance

“…A study by Xu et al (2016) of beef cattle manure in Alberta, Canada, observed that erm (B) and tet (M) abundances were significantly lower in stockpiles 26 d after formation compared with initial abundances (Xu et al, 2016). Conversely, in the present study erm (B) and tet (M) abundances between samples on 0 and 28 d after stockpile formation were not significantly different (Supplemental Table S2).…”

“…Animal manure harbors ARB and ARG regardless of antimicrobial use since manure is densely populated with bacteria (Sharma et al, 2009; Udikovic‐Kolic et al, 2014; Vikram et al, 2017; Xu et al, 2016). Several studies have raised concerns that amending croplands with animal manure, including from animals produced without antimicrobial use, enduringly increases AMR levels in soil, resulting in increased human exposure to AMR via consumption of the produced crops (Ghosh and LaPara, 2007; McKinney et al, 2018; Udikovic‐Kolic et al, 2014).…”

Detection, Occurrence and Fate of Emerging Contaminants in Agricultural Environments

“…Xu et al (2016) compared two management practices for beef cattle manure, stockpiling and window composting, in terms of their effectiveness on reducing antimicrobial resistance genes (ARGs). The levels of sul (1), tet (B), and erm (X) in the manure declined by 0.5, 1.6 and 2.8 log units per gram of dry matter, respectively, after 102 days.…”