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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #317796

Title: Quantifying attachment and antibiotic resistance of Escherichia coli from conventional and organic swine manure

item ZWONITZER, M - Texas A&M University
item SOUPIR, M - Iowa State University
item JARBOE, L - Iowa State University
item Smith, Douglas

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2016
Publication Date: 3/1/2016
Publication URL:
Citation: Zwonitzer, M.R., Soupir, M.L., Jarboe, L.R., Smith, D.R. 2016. Quantifying attachment and antibiotic resistance of Escherichia coli from conventional and organic swine manure. Journal of Environmental Quality. 45(2):609-617. doi:10.2134/jeq2015.05.0245.

Interpretive Summary: Antibiotics are often used in animal diets to minimize diseases in livestock; however, over use of antibiotics is often blamed for the incidence of antibiotic resistant infections in humans. This study was conducted to evaluate the relationship between antibiotic resistance of E. coli bacteria in swine manure and the ability of the E. coli to attach to sediment. Thirteen antibiotics were used to test for antibiotic resistance. Results from this study suggest that there was no relationship between E. coli antibiotic resistance and attachment to sediment in conventional swine facilities (i.e., those that use preventative antibiotics), but the relationship between antibiotic resistance and attachments did exist in “organic” swine facilities (i.e., those that do not feed prophylactic antibiotics). There were no incidences of E. coli colonies that were susceptible to only one antibiotic, thus they were either susceptible to all antibiotics or resistant to multiple antibiotics. The impact of this research is to provide insight to researchers, policy makers and farmers as to the potential impact of feeding low levels of antibiotics to animals on environmental quality as measured by the antibiotic resistant E. coli in manure.

Technical Abstract: Broad spectrum antibiotics, used to treat infections in livestock, are often administered at sub-therapeutic levels in feed rations to promote growth and for prophylaxis. Previous studies have shown that bacteria preferentially attach to sediments affecting their transport in overland flow; however, quantitative understanding regarding the attachment mechanisms and their relationship to antibiotic resistance which may affect human health is mostly unknown. The objective of this study is to examine the relationships between resistance and attachment to sediment in Escherichia coli collected from swine manure. Five hundred and fifty-six colonies were isolated from six farms, two organic and four conventional (antibiotics fed prophylactically). Antibiotic resistance was quantified using 13 antibiotics at three MIC concentrations: resistant, intermediate, and susceptible. Isolates were subjected to an attachment assay. Results show E. coli isolates from conventional systems conferred higher levels of resistance to amoxicillin, ampicillin, chlortetracycline, erythromycin, kanamycin, neomycin, streptomycin, tetracycline, and tylosin. Results also indicate that E. coli isolated from conventional systems attached to quartz at statistically higher levels than those from organic systems. Statistical analysis showed that a significant relationship did not exist between antibiotic resistance levels and attachment in E. coli from conventional systems, but did for organic systems. Better quantification of these relationships is critical to understanding the behavior of E. coli in the environment and preventing exposure of human populations to antibiotic-resistant bacteria. Results may also be important in making manure recommendations to farmers as they pertain to application timing and incorporation.