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ARS Home » Midwest Area » Bowling Green, Kentucky » Food Animal Environmental Systems Research » Research » Publications at this Location » Publication #313591
Title: Composting swine slurry to reduce indicators and antibiotic resistance genes

Author
item Cook, Kimberly - Kim
item Bolster, Carl
item Sistani, Karamat

Submitted to: Waste to Worth Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/16/2015
Publication Date: 3/3/2015
Citation: Cook, K.L., Bolster, C.H., Sistani, K.R. 2015. Composting swine slurry to reduce indicators and antibiotic resistance genes. Waste to Worth Conference. March 30-Aril 3, 2015. Seattle, Washington.

Interpretive Summary: Over the last twenty years there have been considerable increases in the incidence of human infections with bacteria that are resistant to commonly used antibiotics. This has precipitated concerns about the use of antibiotics in livestock production. Composting of swine manure has several advantages, liquid slurries are converted to solid, the total volume of material is reduced and the stabilized product is more easily transported off-site. The goal of this study was to determine if composting can also be used to reduce the concentration of indicators and bacteria containing genes for antibiotic resistance (AR) in swine manure. Compost trials were conducted in either fall (FT) or spring (ST) and piles were turned once, three times or upon reaching 65 ºC. Microbial indicators and populations with AR genes for tetracycline, erythromycin and sulfonamide resistance were quantified by culture and/or quantitative, real-time (qPCR) analysis. In the FT, concentrations of enterococci decreased below culturable detection within 21 days, corresponding with a 99% decrease in detection by qPCR. Similar decreases in qPCR detection in the ST took longer (day 49 or day 77 of composting). Changes in the concentration of bacteria with AR genes varied by antibiotic type (erythromycin (36% - 97%), tetracycline (94% to 99%) and sulfonamide (53% to 84%)) and compost season (greater decreases in ST). There were few differences based on turning regime. These results suggest that composting effectively decreases the concentration of indicators and AR genes in swine manure.

Technical Abstract: Over the last twenty years there have been considerable increases in the incidence of human infections with bacteria that are resistant to commonly used antibiotics. This has precipitated concerns about the use of antibiotics in livestock production. Composting of swine manure has several advantages, liquid slurries are converted to solid, the total volume of material is reduced and the stabilized product is more easily transported off-site. The goal of this study was to determine if composting can also be used to reduce the concentration of indicators and bacteria containing genes for antibiotic resistance (AR) in swine manure. Compost trials were conducted in either fall (FT) or spring (ST) and piles were turned once, three times or upon reaching 65 ºC. Microbial indicators and populations with AR genes for tetracycline, erythromycin and sulfonamide resistance were quantified by culture and/or quantitative, real-time (qPCR) analysis. In the FT, concentrations of enterococci decreased below culturable detection within 21 days, corresponding with a 99% decrease in detection by qPCR. Similar decreases in qPCR detection in the ST took longer (day 49 or day 77 of composting). Changes in the concentration of bacteria with AR genes varied by antibiotic type (erythromycin (36% - 97%), tetracycline (94% to 99%) and sulfonamide (53% to 84%)) and compost season (greater decreases in ST). There were few differences based on turning regime. These results suggest that composting effectively decreases the concentration of indicators and AR genes in swine manure.