Coxiella burnetii

Coxiella burnetii is a tiny gram-negative coccobacillus, staining well according to Giemsa. C. burnetii is the only species of the genus Coxiella and is the causative agent of Q-fever. Due to its low infectious dose and good resistance to drying, Coxiella can be used as a biological weapon.

Morphology

• highly pleiomorphic, small coccobacillus
• the wall is formed similarly to G minus bacteria

Physiology

• intracellular parasites, multiplying only in the phagolysosome of living cells
• multiplies in cells, during the cycle large and small forms alternate and at the same time spore-like formations are formed, which, however, differ in their structure from spores of gram-positive bacteria (described by Czechoslovak authors)

Cultivation

• multiplies at low pH phagolysosome of cells
• grows on common media and yolk sac of chicken embryos
• we prove it by special staining in infected cells

Laboratory diagnostics

• isolation is very dangerous for laboratory workers, and therefore it is performed only in specialized workplaces (VÚ SAV Bratislava, rickettsia department)
• usually, the diagnosis of Q-fever is performed serologically (immunofluorescence, binding Complement, PCR)

Antigens and toxicity

• occurrence in a single antigenic type, but there are alternating two phases:
  • Phase I - virulent strains after fresh isolation
  • II. phase - loss of surface polysaccharides during repeated cultures

Pathogenesis

• the infectious dose is very low, a single cell is enough
• the first infected cell is mostly alveolar macrophages after its decay blood get Coxielly into many organs, and therefore the disease does not only occur in the lungs
• antibodies against the first phase cause Coxiell to disappear from the bloodstream
• cellular immunity is necessary for healing, it fails in a few percent of the infected and the infection then becomes chronic

Epidemiology

• in nature, the source of the infection are various animals (cattle, goats, sheep, ticks), which excrete Coxielly milk, urine, faeces
• the largest amount of Coxiell is found in placentas
• transmission is most often carried out by inhalation of contaminated dust, less often when ingested or processed contaminated products, very rarely transmission by a tick is possible.

Disease

• in about half of the cases, the infection is inapparent, therefore the number of registered diseases is not high
• in other cases it causes an acute infection with an incubation period of 20 days, which is called Q-fever (query = question, because at first etiology was uncertain), it is a typical occupational zoonosis
• Q fever is manifested as a disease similar to influenza, atypical pneumonia (without cough and no expectoration), very rarely as granulomatous hepatitis, splenomegaly
• the chronic form is culture-negative endocarditis

Treatment

• the acute form of Q fever is treated with doxycycline or macrolides
• the chronic form must be treated for at least 18 months with a combination of doxycycline and hydrochloroquine (basifies the content of lysosomes)

Links

Related articles

• Gram stain
• Q fever

External links

• Q-fever (Czech wikipedia)

References

• VOTAVA, Miroslav – BROUKAL, Zdeněk. Lékařská mikrobiologie pro zubní lékaře. 1. edition edition. 2007. ISBN 978-80-86850-03-0.

• BEDNÁŘ, Marek – SOUČEK, Andrej – FRAŇKOVÁ, Věra. Lékařská mikrobiologie : Bakteriologie, virologie, parazitologie. 1. edition. 1999. ISBN 8023802976.