Coxiella

Abstract Co.xi.el'la. M.L. fem. dim. ‐ ella ending; M.L. fem. n. Coxiella named after Harold R. Cox, who in collaboration with G.E. Davis, first isolated this organism in the United States shortly after its discovery in Australia and who introduced the technique of yolk sac inoculation of the chick embryo, which greatly facilitated the study of this and other genera. Strictly intracellular bacteria , usually 0.2–0.4 µm × 0.4–1.0 µm. Best stained by Gimenez staining . They have no flagella or capsule. They live in close natural association with arthropod and vertebrate hosts . The genus includes Coxiella burnetii —the agent of Q fever —and endosymbionts of ticks and aquatic invertebrates. C. burnetii grows well in cultured cell lines and in the yolk sac of chicken embryos, where it undergoes a cycle of development with formation of an endospore‐like body. Coxiella burnetii possesses two antigenic phases : natural virulent phase I and attenuated phase II, which is obtained after passage in cultured cell lines and yolk sac. The organism grows in vacuoles of the host cell rather than in the cytoplasm or the nucleus. C. burnetii phase I vacuoles share characteristics of late‐stage, immature phagosomes whereas C. burnetii phase II vacuoles are bactericidal phagolysosomes. Highly resistant to chemical agents and elevated temperature. Coxiellae occur worldwide in ticks and various vertebrates, including humans. Infection is particularly prevalent in cattle, sheep and goats. Extremely infectious; a single aerosol‐borne organism can cause the human disease Q fever. C. burnetii is one of the ten most feared potential bioterrorism agents . The mol % G + C of the DNA is : 42.7. Type species : Coxiella burnetii (Derrick 1939) Philip 1948, 58 AL ( Rickettsia burnetii (sic) Derrick 1939, 14.) Taxonomic and Nomenclature Notes According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Coxiella is: correct name (last update, February 2025) * . LPSN classification: Bacteria / Pseudomonadati / Pseudomonadota / Gammaproteobacteria / Legionellales / Coxiellaceae / Coxiella The genus Coxiella can also be recovered in the Genome Taxonomy Database (GTDB) as g__Coxiella (version v220) ** . GTDB classification: d__Bacteria / p__Pseudomonadota / c__Gammaproteobacteria / o__Coxiellales / f__Coxiellaceae / g__Coxiella * Meier‐Kolthoff et al. ( 2022 ). Nucleic Acids Res , 50 , D801 – D807 ; DOI: 10.1093/nar/gkab902 ** Parks et al. ( 2022 ). Nucleic Acids Res , 50 , D785 – D794 ; DOI: 10.1093/nar/gkab776