title: Tetracycline Selective Pressure and Homologous Recombination Shape the Evolution of Chlamydia suis: A Recently Identified Zoonotic Pathogen.
abstract: Species closely related to the human pathogen Chlamydia trachomatis (Ct) have recently been found to cause zoonotic infections, posing a public health threat especially in the case of tetracycline resistant Chlamydia suis (Cs) strains. These strains acquired a tet(C)-containing cassette via horizontal gene transfer (HGT). Genomes of 11 Cs strains from various tissues were sequenced to reconstruct evolutionary pathway(s) for tet(C) HGT. Cs had the highest recombination rate of Chlamydia species studied to date. Admixture occurred among Cs strains and with Chlamydia muridarum but not with Ct Although in vitro tet(C) cassette exchange with Ct has been documented, in vivo evidence may require examining human samples from Ct and Cs co-infected sites. Molecular-clock dating indicated that ancestral clades of resistant Cs strains predated the 1947 discovery of tetracycline, which was subsequently used in animal feed. The cassette likely spread throughout Cs strains by homologous recombination after acquisition from an external source, and our analysis suggests Betaproteobacteria as the origin. Selective pressure from tetracycline may be responsible for recent bottlenecks in Cs populations. Since tetracycline is an important antibiotic for treating Ct, zoonotic infections at mutual sites of infection indicate the possibility for cassette transfer and major public health repercussions.
authors: Department of Medicine, Division of Infectious Diseases and Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA.
authors: Sandeep J
authors: SJ
authors: Joseph
authors: Center for Immunobiology and Vaccine Development, UCSF Benioff Children's Hospital Oakland Research Institute, Oakland, CA, USA.
authors: Hanna
authors: H
authors: Marti
authors: Department of Infectious Disease Epidemiology, Imperial College, London, United Kingdom.
authors: Xavier
authors: X
authors: Didelot
authors: Department of Medicine, Division of Infectious Diseases and Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, USA.
authors: Timothy D
authors: TD
authors: Read
authors: Center for Immunobiology and Vaccine Development, UCSF Benioff Children's Hospital Oakland Research Institute, Oakland, CA, USA Joint Graduate Program in Bioengineering, University of California, San Francisco and University of California, Berkeley, CA, USA ddean@chori.org.
authors: Deborah
authors: D
authors: Dean
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D020562:Betaproteobacteria / Q000187:drug effects / Q000235:genetics; D002689:Chlamydia / Q000187:drug effects / Q000235:genetics*; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D059765:Homologous Recombination; D012641:Selection, Genetic; D013752:Tetracycline / Q000494:pharmacology; D013753:Tetracycline Resistance / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D013752:Tetracycline
keywords: Chlamydia suis; comparative genomics; genomic diversification; tet(C)-containing cassette; tetracycline selective pressure