Location: Food and Feed Safety Research
Title: Pathogen prevalence and influence of composted dairy manure application on antimicrobial resistance profiles of commensal soil bacteria Authors
|Fox, W - TX WATER RESOURCES INST|
|Hoffman, D - BLACKLAND RESEARCH STAT|
Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2008
Publication Date: February 1, 2009
Citation: Edrington, T.S., Fox, W.E., Callaway, T.R., Anderson, R.C., Hoffman, D.W., Nisbet, D.J. 2009. Pathogen prevalence and influence of composted dairy manure application on antimicrobial resistance profiles of commensal soil bacteria. Foodborne Pathogens and Disease. 6:217-224. Interpretive Summary: The land application of composted cattle manure has numerous benefits. However, as cattle are naturally infected with bacteria that cause food sickness in humans, it is important to make sure this is a safe practice. Additionally, these bacteria can become resistant to medicine used to treat infections and can pass this resistance to other bacteria. Therefore, we took multiple samples of composted dairy manure and analyzed them for E. coli O157:H7 and Salmonella. All compost samples were negative for these bacteria. We also collected soil samples from land that had been treated with composted manure and looked at antimicrobial resistance patterns of common soil bacteria. No differences were observed in bacteria obtained after compost application. Results from this research support the use of composted cattle manure as an environmentally safe practice.
Technical Abstract: Manure production and its subsequent disposal is a continual problem for the livestock producer. Composting manure, if done properly should kill pathogenic bacteria such as Salmonella and E. coli O157:H7, providing for an environmentally safe product. Recently, large scale application of composted manure to aid in land restoration has been evaluated on damaged rangeland. While the benefits of this practice could be substantial, it is crucial to ensure that such large scale applications are safe and harmonious with the environment. Over a three-year period, samples of composted dairy manure, representing 11 composting operations (2-6 samples/producer; 100 total samples), were screened for Salmonella and E. coli O157:H7 and were all culture negative. However, some non-pathogenic bacteria were cultured from these compost samples that could theoretically facilitate the spread of antimicrobial resistance from the dairy to compost application sites. Therefore, we collected soil samples (3 samples/plot; 10 plots/treatment; 90 total samples) from rangeland that received either composted dairy manure (CP), commercial fertilizer (F), or no treatment (control, CON). Two collections were made appoximately 2 and 7 months following treatment application. Soil samples were cultured for Pseudomonas and Enterobacter and confirmed isolates subjected to antimicrobial susceptibility testing. Three species of Enterobacter [cloacae (27 isolates), aeroginosa (2 isolates), and sakazakii (1 isolate),] and two species of Pseudomonas [aeruginosa (11 isolates) and putida (7)] were identified. Five Enterobacter isolates were resistant to ampicillin and one isolate was resistant to spectinomycin. All Pseudomonas isolates were resistant to ampicillin, ceftiofur, florfenicol, sulphachloropyridazine, sulphadimethoxine, and trimethoprim/sulfamethoxazole and most isolates were resistant to chlortetracycline and spectinomycin. Pseudomonas isolates were resistant to an average of 8.6, 7.9 and 8 antibiotics for CON, CP, and F treatments, respectively. No treatment differences were observed in antimicrobial resistance patterns in any of the soil isolates examined. Results reported herein support the use of composted dairy manure as an environmentally friendly soil amendment.