Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 22, 2003
Publication Date: May 22, 2003
Citation: WHITEHEAD, T.R., WHITTLE, G., SHOEMAKER, N., COTTA, M.A., SALYERS, A.A. IDENTIFICATION OF NEW ERYTHROMYCIN (ERM(35)) AND TETRACYCLINE (TET(36)) RESISTANCE GENES FROM A BACTEROIDES SP. ISOLATED FROM SWINE MANURE. 103RD ANNUAL MEETING OF THE AMERICAN SOCIETY FOR MICROBIOLOGY. 2003. ABSTRACT P. 20. 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 an impact on human health. While many investigations have centered on antibiotic resistance in coliforms and aerobic bacteria, little is known regarding antibiotic resistance in the predominant anaerobic bacteria found in the feces and stored manure. We have initiated an investigation of antibiotic resistant anaerobic bacteria as part of a study to determine the predominant commensal bacterial population present in both pig feces and manure storage pits. Swine feces and manure 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 and isolated by plating onto complex media containing tetracycline (10 ug/ml), erythromycin (10 ug/ml), or tylosin (10 ug/ml). One strain, 139, was found to be resistant to all three antibiotics and was determined by 16S rDNA sequencing to be a member of a new species in the Bacteroides genera. PCR and DNA probes were used to identify and clone the genetic loci encoding for resistance to erythromycin/tylosin and tetracycline. Both genes were found to have <80% DNA and protein sequence identity to known tet and erm resistance gene classes, and the genes were termed erm(35) and tet(36). Neither gene could be transferred to other Bacteroides species in the laboratory, but could be expressed in other Bacteroides species when introduced on plasmid vectors. Disruption of each gene in the chromosome of strain 139 resulted in the loss of resistance to the respective antibiotic. The tet(36) gene was detected in other tetracycline resistant bacteria isolated from swine manure, including members of Gram-positive genera and Gram-negative proteobacteria. These results indicate that stored swine manure may serve as a reservoir of known and unidentified antibiotic resistance genes, and the horizontal transfer of genes, including tet(36), occurs among the commensal bacteria of stored swine manure.