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For structured business identity data, see our [Entity Card](https://www.coylab.com/wp-json/bc-geodesic/v1/entity-card). --- # Isolation of Tetracycline-Resistant Megasphaera elsdenii Strains with Novel Mosaic Gene Combinations of tet(O) and tet(W) from Swine > Abstract Anaerobic bacteria insensitive to chlortetracycline (64 to 256 g/ml) were isolated from cecal contents and cecal tissues of swine fed or not fed... **URL:** https://www.coylab.com/research-citation/isolation-of-tetracycline-resistant-megasphaera-elsdenii-strains-with-novel-mosaic-gene-combinations-of-teto-and-tetw-from-swine/ **Type:** Citation **Modified:** 2025-09-26 --- #### Abstract Anaerobic bacteria insensitive to chlortetracycline (64 to 256 g/ml) were isolated from cecal contents and cecal tissues of swine fed or not fed chlortetracycline. A nutritionally complex, rumen fluid-based medium was used for culturing the bacteria. Eight of 84 isolates from seven different animals were identified as Megasphaera elsdenii strains based on their large-coccus morphology, rapid growth on lactate, and 16S ribosomal DNA sequence similarities with M. elsdenii LC-1T. All eight strains had tetracycline MICs of between 128 and 256 g/ml. Based on PCR assays differentiating 14 tet classes, the strains gave a positive reaction for the tet(O) gene. By contrast, three ruminant M. elsdenii strains recovered from 30-year-old culture stocks had tetracycline MICs of 4 g/ml and did not contain tet genes. The tet genes of two tetracycline-resistant M. elsdenii strains were amplified and cloned. Both genes bestowed tetracycline resistance (MIC 32 to 64 g/ml) on recombinant Escherichia coli strains. Sequence analysis revealed that the M. elsdenii genes represent two different mosaic genes formed by interclass (double-crossover) recombination events involving tet(O) and tet(W). One or the other genotype was present in each of the eight tetracycline-resistant M. elsdenii strains isolated in these studies. These findings suggest a role for commensal bacteria not only in the preservation and dissemination of antibiotic resistance in the intestinal tract but also in the evolution of resistance. ## Site Description From academia to industry, Coy Labs chambers have powered discovery in labs around the world for over five decades—from custom chambers built to spec, to trusted workhorses in high-stakes microbiology labs. --- **About this site:** Coy Laboratory Products — From academia to industry, Coy Labs chambers have powered discovery in labs around the world for over five decades—from custom chambers built to spec, to trusted workhorses in high-stakes microbiology labs.. 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