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ARS Home » Plains Area » Lincoln, Nebraska » Agroecosystem Management Research » Research » Publications at this Location » Publication #305723
Title: Characterization of antibiotic resistant (AR) fecal indicators in runoff from fields amended with swine manure

Author
item Durso, Lisa
item Gilley, John
item Woodbury, Bryan
item Parker, David

Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/28/2014
Publication Date: 11/4/2014
Citation: Durso, L.M., Gilley, J.E., Woodbury, B.L., Parker, D.B. 2014. Characterization of antibiotic resistant (AR) fecal indicators in runoff from fields amended with swine manure[abstract]. Abstracts from the ASA-CSSA-SSSA International Annual Meeting November 2-5, 2014, Long Beach, California. 254-1.

Interpretive Summary: Animal manures are commonly applied to agricultural fields to provide nutrients and improve soil quality. One concern associated with food animal manures is the introduction of antibiotic drugs, antibiotic resistant bacteria, and antibiotic resistance genes that may be spread in the environment, soil, and water, with the potential to adversely impact the treatment of human disease. In this study we measure two different types of antibiotic resistant bacteria in swine manure that is applied to an agricultural field, and count how many bacterial cells from the manure are carried away after a rainfall event. We look specifically at “fecal indicator bacteria”. These are bacteria that are frequently associated with feces, such as E. coli, total coliforms, and Enterococcus. We measure the number of fecal indicator bacteria in the swine manure, the number in the soil before the manure is applied, and the number in runoff from three different simulated rainfall events that occur 24, 48, and 72 hours after the manure is placed on the field. We also measure the number of these bacteria that are resistant to tetracycline, and the number resistant to bacitracin, and then we characterize individual bacterial isolates to see if any of them are resistant to multiple different types of antibiotics. Tetracycline resistance was common in the source manure for both Gram negative and Gram positive fecal indicators, and tetracycline resistant bacteria were commonly isolated from the runoff. Most pre-application soils were negative for tetracycline resistant fecal indicators. No bacitracin resistant organisms were isolated. Multiply drug resistant (MDR) fecal indicators were present in both the source manure and in runoff. In general, the runoff isolates had similar MDR patterns to the source manure, although some heterogeneity was observed. In conclusion, AR bacteria from swine manure can persist on agricultural fields, and be transported from agricultural fields in runoff. The types of bacteria and drugs being measured impacts the results, and data from this study support the idea that the amount of AR bacteria detected depends on the specific type of resistance being measured.

Technical Abstract: The application of animal manures to agricultural soil is a widespread practice. One concern associated with food animal manures is the introduction of antibiotic drugs, AR bacteria, and AR genes that may be spread through and across agroecosystems, with the potential to adversely impact the treatment of human disease. Despite this widespread concern, there is very little information available regarding the numbers and types of resistant bacteria in specific agricultural ecosystems, or data regarding relationships between different types of resistance. In this study, two types of AR bacteria were quantified in runoff from fields amended with swine manure, and characterized for resistance to twelve common antibiotic drugs. Swine manure was broadcast onto 0.75 m x 4 m plots containing Aksarben silty clay loam soil. Tetracycline and bacitracin-resistant fecal indicator bacteria were enumerated from the source manure and soil before manure application, and from runoff that was collected on three consecutive days post-manure application, for a total of 52 samples. Isolates were characterized using standard disk diffusion assays. Tetracycline resistance was common in the source manure for both Gram negative and Gram positive fecal indicators, and tetracycline resistant bacteria were commonly isolated from the runoff. Most pre-application soils were negative for tetracycline resistant fecal indicators. No bacitracin resistant organisms were isolated. Multiply drug resistant (MDR) fecal indicators were present in both the source manure and in runoff. In general, the runoff isolates had similar MDR patterns to the source manure, although some heterogeneity was observed. In conclusion, AR bacteria from swine manure can persist on agricultural fields, and be transported from agricultural fields in runoff. The types of bacteria and drugs being measured impacts the results, and data from this study support the idea that the amount of AR bacteria detected depends on the specific type of resistance being measured.