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Syst Appl Microbiol. 2015 Mar;38(2):99-103. doi: 10.1016/j.syapm.2014.12.004. Epub 2015 Jan 8.

Emendation of the family Chlamydiaceae: proposal of a single genus, Chlamydia, to include all currently recognized species.

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Institute of Molecular Pathogenesis, Friedrich-Loeffler-Institut (Federal Research Institute for Animal Health), Jena, Germany. Electronic address:
Department of Microbial Pathogenesis, University of Maryland, Baltimore, MD, USA.
Department of Pathobiology, College of Veterinary Medicine, Auburn University, Auburn, AL, USA.
Program in Infectious Diseases, University of California, Berkeley, CA, USA.
University of Washington, Seattle, WA, USA.
Mediterranean Institute for Advanced studies (IMEDEA, CSIC-UIB), Esporles, Illes Balears, Spain.
Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria.


The family Chlamydiaceae (order Chlamydiales, phylum Chlamydiae) comprises important, obligate intracellular bacterial pathogens of humans and animals. Subdivision of the family into the two genera Chlamydia and Chlamydophila has been discussed controversially during the past decade. Here, we have revisited the current classification in the light of recent genomic data and in the context of the unique biological properties of these microorganisms. We conclude that neither generally used 16S rRNA sequence identity cut-off values nor parameters based on genomic similarity consistently separate the two genera. Notably, no easily recognizable phenotype such as host preference or tissue tropism is available that would support a subdivision. In addition, the genus Chlamydophila is currently not well accepted and not used by a majority of research groups in the field. Therefore, we propose the classification of all 11 currently recognized Chlamydiaceae species in a single genus, the genus Chlamydia. Finally, we provide emended descriptions of the family Chlamydiaceae, the genus Chlamydia, as well as the species Chlamydia abortus, Chlamydia caviae and Chlamydia felis.


Chlamydiaceae; Classification; Single genus Chlamydia

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