Molecular testing for rickettsiae is used for the laboratory documentation of rickettsioses.
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Rickettsia is a genus of Gram-negative bacteria that are pleomorphic, mobile, rod-shaped, and obligately intracellular. The genomes of Rickettsia species consist of a single circular DNA chromosome usually up to 1 Mbp (million base pairs). These genomes consist of 900 to 1500 genes per species, of which 743 genes are common to all genomes of the Rickettsia species studied to date.
Rickettsia species can be classified into the following groups based on the severity of the infections they cause:
- Spotted Fever Group
- Typhoid Group
- Bush Typhus Group (Tsutsugamushi disease)
Rickettsia species are transmitted by ticks, fleas, and lice and transmitted to humans through bites from infected arthropods. Rickettsiae adhere to the endothelial lining of the vascular system using adhesins (proteins of their outer membrane), then they are phagocytosed, resulting in their invasion of the host cell. Once inside the cell, the bacteria multiply, resulting in the lysis of the host cell due to the accumulation of a large number of bacteria (typhus) or escape from the cells causing damage to the membrane and resulting in water influx (spotted fever). In particular, the entry of Rickettsia into the endothelial cells that line the blood vessels results in the appearance of Rocky Mountain spotted fever (RMSF).
Infection with various species of Rickettsia can cause typhus, Mediterranean spotted fever, Rocky Mountain spotted fever, and Q fever with common symptoms such as skin rash, headache, neurological symptoms, heart failure, and shock. Rocky Mountain spotted fever specifically causes bleeding, inflammation, and blood clot formation. Infection with the most virulent Rickettsia species (Rickettsia rickettsii and Rickettsia prowazekii) has a high mortality rate if treatment is not given early in the infection.
Tetracyclines are the drug of choice in the treatment of rickettsial infections. No vaccines are available.
For the molecular test for Rickettsia, primers are used that recognize the following microorganisms:
- Rickettsia rickettsii
- Rickettsia typhi (mooseri)
- Rickettsia conorii
- Rickettsia prowazekii
- Rickettsia akari
- Rickettsia australis
- Rickettsia honei
- Rickettsia marmionii
- Rickettsia sibirica
Important Note
Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. The correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".
Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings, and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.
At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.
