The agent of Q fever, Coxiella burnetii, is a minuté pleomorphic gram-negative coccobacillus. It belongs to the most resistant bacteria and is námely resistant to desiccation. It can therefore become a dangerous bio-logical weapon. It propagates intracellularly only, námely in the phagolysosomes. There has been described a developmental cycle in coxiellae, that includes macrocellular and microcellular forms and the formation of spore-like bodies. In the laboratory, coxiellae can be propagated in the yolk sac of chick embryos, in cell cultures, and in experimental animals, however, those procedures involve a great risk of laboratory infecti-on. By passaging in the laboratory the virulent antigenic phase I passes to phase II which corresponds roughly to the R-phase in common bacteria. Acute infection mostly takés the course of atypical pneumonia, a flu-like affection, hepatitis, or chronic endocarditis. Q fever is a typical zoonosis, mostly profession-lin-ked, the respiratory tract being the chief portál of entry. The remedy of choice are broad-spectrum antibio-tics. Routine laboratory diagnostics is based on the presence of antibodies, more recently direct demonstra-tion by the polymerase chain reaction has been recommended.

        Key words: Coxiella burnetii - Q fever - microbiology.