Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2003
Publication Date: 7/1/2003
Citation: WHITTLE, G., WHITEHEAD, T.R., HAMBURGER, N., SHOEMAKER, N.B., COTTA, M.A., SALYERS, A.A. IDENTIFICATION OF A NEW RIBOSOMAL PROTECTION TYPE OF TETRACYCLINE RESISTANCE GENE, TET(36), FROM SWINE MANURE PITS. APPLIED AND ENVIRONMENTAL MICROBIOLOGY. 2003. V. 69. P. 4151-4158. Interpretive Summary: 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 an impact on human health. While many investigations have centered on antibiotic resistance in coliforms and other aerobic bacteria, less attention has been directed towards investigating antibiotic resistance in the anaerobic microflora found in the feces and stored manure of domestic animals which may serve as reservoirs of antibiotic resistance genes. As part of our project determining the bacterial populations of swine feces and manure storage pits in relation to odor production, we investigated potential antibiotic resistance in anaerobic bacteria present in these ecosystems. We now report on the isolation of a previously unidentified Bacteroides species from swine manure that is resistant to tylosin, erythromycin, and tetracycline. This strain contains a novel tetracycline resistance gene that represents a new gene class.
Technical Abstract: Prior to this work, only one ribosome protection type of tetracycline resistance gene, tetQ, had been identified in Bacteroides spp. During an investigation of anaerobic bacteria present in swine feces and manure storage pits, a tetracycline resistant Bacteroides strain was isolated. Subsequent analysis showed that this new Bacteroides strain 139 did not contain tetQ, but contained a previously unidentified tetracycline resistance gene. Sequence analysis showed that the tetracycline resistance gene from Bacteroides strain 139 encoded a protein that defines a new class of ribosome-protection type of tetracycline resistance, designated Tet 36. Tet 36 has 60% amino acid identity over 640 amino acids to TetQ and between 31% and 49% amino acid identity to the nine other ribosome protection-type of tetracycline resistance genes. The tet(36) region was not observed to transfer from Bacteroides strain 139 to another Bacteroides sp. under laboratory conditions. Yet tet(36) was found in other genera of bacteria isolated from the same swine manure pits. Phylogenetic analysis of the tet(36)-containing isolates indicated that tet(36) was present not only in the Cytophaga-Flavobacter-Bacteroides (CFB) group to which Bacteroides sp. 139 belongs, but also was present in Gram-positive genera and Gram-negative proteobacteria, indicating that horizontal transfer of tet(36) is occurring between these divergent phylogenetic groups in the farm environment.