Submitted to: American Society for Microbiology
Publication Type: Abstract Only
Publication Acceptance Date: May 25, 2000
Publication Date: N/A
Technical Abstract: Antimicrobial compounds have been commonly used as feed additives for domestic animals to reduce infection and promote growth. Recent reports have suggested such feeding practices may result in increased microbial resistance to antibiotics, which can have impact on human health. Little is known regarding antibiotic resistance in anaerobic bacteria found in the efeces and stored manure. We have initiated an investigation of antibiotic resistant anaerobic bacteria as part of a study to determine the predominant bacterial population present in pig feces and waste storage pits. Samples were collected from a local swine production facility where tylosin was the only antibiotic added to the feed. Antibiotic resistant bacteria were enumerated by plating onto complex media with and without tetracycline, erythromycin, tylosin, or vancomycin. Antibiotic resistant organisms were found in all samples, and the level of resistance ranged from 4% erythromycin resistance to 32% tylosin resistance. Pure cultures of antibiotic resistant bacteria were isolated for identification and further characterization. All tylosin resistant bacteria tested were also resistant to erythromycin. Erythromycin and tylosin resistant strains were subjected to PCR tests for the presence of erm genes. One tylosin resistant strain was found to contain at least two plasmids. One of the plasmids was able to replicate and provide erythromycin and tylosin resistance in Bacillus subtilis, Escherichia coli, and Streptococcus gordonii. The finding of a high number of identified and unidentified antibiotic resistant eubacteria in swine feces and waste storage pits suggests that these ecosystems may serve as a potential reservoir of antibiotic resistance genes.