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United States Department of Agriculture

Agricultural Research Service

Title: Tetracycline Resistant Bacteria in Soil from Manure-Applied Cropland

Authors
item Thurston Enriquez, Jeanette
item Tarkelson, David - U NEBRASKA,LINCOLN
item Payero, Jose - U NEBRASKA,LINCOLN
item MCGHEE, JENNIFER
item Johnson, Derek
item Kahler, Amy

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 1, 2004
Publication Date: May 1, 2004
Citation: Thurston-Enriquez, J., Tarkelson, D., Payero, J., Frohner, J., Johnson, D., and Kahler, A. 2004. Tetracycline resistant bacteria in soil from manure-applied cropland. In: Proceedings of the American Society for Microbiologists. 104th American Society for Microbiologists General Meeting, May 23-27, 2004, New Orleans, LA. 2004 CDROM.

Interpretive Summary: Antibiotics, such as tetracycline, are frequently given to livestock in order to reduce infection and promote growth. Since tetracycline can be excreted unchanged in feces and urine, land application of livestock manure may influence tetracycline resistant bacterial populations present in soil and water. The purpose of the following study was to determine the effect that cattle manure has on tetracycline resistant bacterial populations in cropland soil. Soil that was treated with manure originating from cattle treated with tetracycline had higher levels than soil treated with inorganic fertilizer. Tetracycline resistant bacteria, however, were detected in both types of treated soils. Numbers of tetracycline resistant bacteria declined over time in soil collected from manure-applied plots whereas no significant trend was observed for inorganic fertilizer-applied plots. These results suggest that manure originating from tetracycline-fed cattle influences levels of tetracycline resistant bacteria in soil where the manure is applied.

Technical Abstract: Antibiotics are frequently given to livestock in order to reduce infection and promote growth. Since they can be excreted unchanged in feces and urine, land application of livestock manure may influence antibiotic resistant bacterial populations present in soil and water. The purpose of the following study was to determine the effect that cattle manure has on antibiotic resistant bacterial populations in cropland soil. Manure was collected from a pen of 10 calves that received 75mg/head/day of oxytetracycline. This manure was applied to 20 x 30 ft plots that were continuously planted with corn. Cattle manure-applied plots, two replicates each, were studied: a) residual manure (applied 15 months prior to sampling) and b) freshly-applied manure (applied 3 months prior to sampling). Control plots, applied with only inorganic fertilizer, were also sampled. Soil samples (top 2 inches) were analyzed for tetracycline resistant bacteria. Tetracycline resistant bacteria were recovered from soil samples by spread-plating diluted samples onto R2A agar containing 16-ug/ml tetracycline. Geometric average concentrations of tetracycline resistant heterotrophic bacteria recovered from soil that was collected from freshly applied manure, residual manure, and inorganic fertilizer-applied plots contained 1.15 x 106 colony forming units (CFU)/gram, 1.17 x 106 CFU/gram, and 2.01 x 105 CFU/gram, respectively. There were no significant differences (P>0.05) in tetracycline resistant bacterial concentrations between the two manure treatments. Significantly (P<0.05) lower numbers of tetracycline resistant heterotrophic bacteria, however, were recovered from inorganic fertilizer compared to manure-applied plots. Furthermore, numbers of tetracycline resistant heterotrophic bacteria declined over time in soil collected from manure-applied plots whereas no significant trend was observed for inorganic fertilizer-applied plots. These results indicate that manure originating from tetracycline-fed cattle influences levels of tetracycline resistant bacteria in soil where the manure is applied.

Last Modified: 9/29/2014
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