Antimicrobial Use and Resistance in Swine Waste Treatment Systems

Abstract

Chlortetracycline and the macrolide tylosin were identified as commonly used antimicrobials for growth promotion and prophylaxis in swine production. Resistance to these antimicrobials was measured throughout the waste treatment processes at five swine farms by culture-based and molecular methods. Conventional farm samples had the highest levels of resistance with both culture-based and molecular methods and had similar levels of resistance despite differences in antimicrobial usage. The levels of resistance in organic farm samples, where no antimicrobials were used, were very low by a culture-based method targeting fecal streptococci. However, when the same samples were analyzed with a molecular method detecting methylation of a specific nucleotide in the 23S rRNA that results in resistance to macrolides, lincosamides, and streptogramin B (MLS B ), an unexpectedly high level of resistant rRNA (approximately 50%) was observed, suggesting that the fecal streptococci were not an appropriate target group to evaluate resistance in the overall microbial community and that background levels of MLS B resistance may be substantial. All of the feed samples tested, including those from the organic farm, contained tetracycline resistance genes. Generally, the same tetracycline resistance genes and frequency of detection were found in the manure and lagoon samples for each commercial farm. The levels of tetracycline and MLS B resistance remained high throughout the waste treatment systems, suggesting that the potential impact of land application of treated wastes and waste treatment by-products on environmental levels of resistance should be investigated further.

Effects of the antimicrobial tylosin on the microbial community structure of an anaerobic sequencing batch reactor

“…Angenent et al (2008) reported an increase in MLS B resistance in an ASBR treating swine waste but attributed their results to the enrichment with resistant bacteria present in the reactor feed. Occurrence of macrolide resistant organisms in swine waste has been reported previously (Chen et al, 2010;Holzel et al, 2010;Jindal et al, 2006). These results suggest that the development of MLS B resistance can be influenced by historical exposure of the seed sludge to antimicrobials and antimicrobial resistant microorganisms and the presence of antimicrobial resistant microorganisms in the influent.…”

“…Waste streams from hospitals, animal husbandry, and pharmaceutical production facilities contain elevated concentrations of antimicrobials (Campagnolo et al, 2002;Kummerer, 2001;Zilles et al, 2005) and are commonly treated in systems that rely on biological processes. Acceptable treatment performance has been reported in anaerobic lagoons treating manure with concentrations of antimicrobials that would inhibit sensitive microorganisms (Jindal et al, 2006;Zilles et al, 2005), but the mechanism(s) for maintaining biological activity in the presence of antimicrobials and the associated questions of how and when antimicrobial resistance develops are not well understood.…”

Fate of antimicrobials and antimicrobial resistance genes in simulated swine manure storage

“…Bacitracin A, chlortetracycline, and tylosin are antimicrobials commonly used in swine production (Cromwell, 2002;Jindal et al, 2006) and antimicrobial excretion rates of up to 90% in urine and 75% in feces have been reported (Halling-Sørensen et al, 2001). Swine produced at confined animal feeding operations (CAFOs) typically use one of three waste handling systems: flush systems, pit recharge, or deep pits (Sarmah et al, 2006).…”

Understanding the contribution of environmental factors in the spread of antimicrobial resistance

“…The application of animal waste (biosolids) to agricultural soils (as soil conditioner) is commonly practised in the United States, Europe and Australia [47], and this acts as an entry point of both antibiotics and genetic resistance determinants into the environment [7,29,48]. Enteric bacteria can remain persistent in the environment for weeks to months, depending on species and temperature.…”