Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: July 12, 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 may have impact on human health. We have initiated an investigation of antibiotic resistant anaerobic bacteria as part of a study to determine the predominant bacterial population present in both pig feces and waste storage pits. Fecal and waste storage pit 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 containing either rumen fluid or swine waste slurry and on the same medium containing tetracycline, erythromycin, tylosin, or vancomycin. Antibiotic resistant bacteria were found in all samples. Pure cultures of antibiotic resistant bacteria were isolated for identification by 16S rDNA sequence analyses and further characterization of antibiotic resistance. Several erythromycin and tylosin resistant strains were also tetracycline resistant. When tested by PCR for ermA, ermB, or ermC resistance genes, a number of strains produced products whose DNA sequences demonstrated high sequence identity with known erm resistance genes. One tylosin resistant strain was found to contain a plasmid which was able to replicate and provide erythromycin and tylosin resistance in Bacillus subtilis, Escherichia coli, and Streptococcus gordonii. The presence 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 potential reservoirs of antibiotic resistance genes.