Variations in bacterial community structure and antimicrobial resistance genes abundance in cattle manure and poultry litter

Authors: GURMESSA, BIYENSA - Polytechnic University Of Marche; Ashworth, Amanda; YANG, YICHAO - University Of Arkansas; SAVIN, MARY - University Of Arkansas; Moore, Philip; RICKE, STEVEN - University Of Arkansas; CORTI, GIUSEPPE - Polytechnic University Of Marche; FOPPA PEDRETTI, ESTER - Polytechnic University Of Marche; COCCO, STEFANIA - Polytechnic University Of Marche

Submitted to: Environmental Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2021
Publication Date: 3/24/2021
Citation: Gurmessa, B., Ashworth, A.J., Yang, Y., Savin, M., Moore Jr, P.A., Ricke, S.C., Corti, G., Foppa Pedretti, E., Cocco, S. 2021. Variations in bacterial community structure and antimicrobial resistance genes abundance in cattle manure and poultry litter. Environmental Research. https://doi.org/10.1016/j.envres.2021.111011.
DOI: https://doi.org/10.1016/j.envres.2021.111011

Interpretive Summary: Both cattle manure and poultry litter contain excellent sources of nutrients and as such are used as fertilizers for pastures and crops. Although, there is possible environmental risk in land application from these two manure types, as they can be potential sources of pathogens and antimicrobial resistance (AMR) genes to the environment. Therefore, researchers set out to evaluate 1) the microbial composition of cattle manure and poultry litter, 2) the abundance of antibiotic resistant genes from these two manure sources, and 3) if bacterial diversity is linked to any physical and chemical properties of the two manure sources. The results showed poultry litter had lower bacterial diversity and abundance of AMR genes compared to cattle manure, indicating lower environmental health risks from using poultry litter compared to cattle manure, while supplying greater amounts of nutrients. Study results indicate best management practices are needed to reduce the release of bacteria and AMR genes from cattle manure to soil.

Technical Abstract: Cattle manure and poultry litter are widely used as fertilizers because they are rich sources of nutrients; however, potential adverse environmental effects exist, mainly due to the release of zoonotic bacteria and antimicrobial resistance (AMR) genes. This study was conducted to understand linkages between physiochemical composition, bacterial diversity, and AMR gene presence of cattle manure and poultry litter using Quantitative PCR (Q-PCR) to enumerate four AMR genes (ermB, sulI, intlI, and blactx-m-32), Illumina sequencing of the 16S region, and analysis of physical and chemical properties. Principal coordinate analysis of Bray–Curtis distance revealed distinct bacterial community structures between the two manure sources. Greater alpha diversity occurred in cattle manure compared to poultry litter (P < 0.05). Redundancy analysis showed a strong relationship between manure physiochemical and composition and bacterial abundance, with positive relationships among electrical conductivity, soluble Fe and C/N ratio, and negative associations between total solids and soluble fractions of heavy metals. Cattle manure had the greater abundance of macrolide (ermB) and sulfonamide (sulI) resistant genes. Consequently, fresh cattle manure applications may result in greater potential spread of AMR genes to the soil-water environment (relative to poultry litter), and best management strategies may be needed to reduce the release of zoonotic bacteria and AMR genes before applying manure to soil.