Submitted to: Canadian Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/23/2007
Publication Date: 6/1/2007
Citation: Brooks, J.P., Maxwell, S.L., Rensing, C., Gerba, C.P., Pepper, I.L. 2007. Occurrence of antibiotic-resistant bacteria and endotoxin associated with the land application of biosolids. Canadian Journal of Microbiology. 53:616-622.
Interpretive Summary: When wastewater treatment plants separate large amounts of organic matter from incoming wastewater, the produced byproduct is known as sludge. This sludge is then further treated to reduce pathogen load, producing biosolids. Biosolids can then be disposed of via a number of ways, the most currently environmentally friendly method being land application of biosolids to agricultural land. Though pathogen concentrations can be effectively reduced in biosolids, antibiotic resistant microorganism and endotoxin (bacterial by-product) concentrations may not be reduced. The purpose of this study was to determine the prevalence of antibiotic resistant bacteria and endotoxin in soil following land application of biosolids. Soil samples were collected from a field in which biosolids were applied at typical agricultural rates and these samples were analyzed for the presence of antibiotic resistant microorganisms and endotoxin. Despite the application of the biosolids, little to no change in the overall antibiotic resistant microorganisms and endotoxin was noted throughout the 15 month monitoring period. This study determined and established a baseline understanding of the overall effect that land application of biosolids had on the land-applied field with respect to antibiotic resistant bacterial and endotoxin soil concentrations.
Technical Abstract: The purpose of this study was to determine the prevalence of antibiotic resistant bacteria and endotoxin in soil following land application of biosolids. Soil was collected over a 15 month period following land application of biosolids, and antibiotic resistance was ascertained using clinically relevant antibiotic concentrations. Ampicillin, cephalothin, ciprofloxacin, and tetracycline resistance were all monitored separately for any changes throughout the 15 month period. Endotoxin soil concentrations were monitored using commercially available endotoxin analysis reagents. Overall, land application of biosolids did not increase the percentage of antibiotic resistant culturable bacteria above background soil levels. Likewise land application of biosolids did not significantly increase the concentration of endotoxin in soil. This study determined and established a baseline understanding of the overall effect that land application of biosolids had on the land-applied field with respect to antibiotic resistant bacterial and endotoxin soil densities.