Nucleotide fragments capable of hybridizing specifically to rick

Details Nucleotide fragments capable of hybridizing specifically to rick Nucleotide fragments capable of hybridizing specifically to rick

1996-07-08

1999-11-02

Jones, W. Gary

Chemistry: molecular biology and microbiology

Measuring or testing process involving enzymes or...

Involving nucleic acid

536 231, 536 243, 935 76, 935 77, 935 78, C12Q 168, C07H 2102, C07H 2104, C12N 1500

Patent

active

059767910

DESCRIPTION:

BRIEF SUMMARY
The present invention falls within the field of techniques for the detection and/or identification of bacteria of the genus Rickettsia and more particularly of those using a genetic marker.
Rickettsias are Gram-negative bacteria which belong to the order Rickettsiales and to the family Rickettsiaceae comprising especially the subfamily Rickettsieae which is subdivided into three genera: Coxiella, of which the only known species is Coxiella burnetti; Rickettsia, including all the other species which are pathogenic to man and animals; and Rochalimea. The genus Rickettsia comprises three subgroups: the typhus group to which R. typhi, responsible for endemic typhus, R. prowazekii, responsible for epidemic typhus, and R. canada belong; the scrub typhus group to which R. tsutsugamushi belongs; and the eruptive fever group to which R. rickettsii, R. siberica, R. conorii, R. australis, R. akari, R. montana and R. rhipicephali in particular belong.
Rickettsias are intracellular parasitic bacteria which multiply in the nucleus and the cytoplasm of the host cells for the strains of the eruptive fever group and in the cytoplasm of these cells for the strains of the other groups. The transmission of the bacteria to man occurs through haematophagous insects such as ticks for R. tsutsugamushi (rickettsia of the eruptive fever group), lice for R. prowazekii or flea for R. typhi, during a blood meal followed by dejecta at the site of the bite.
Epidemic typhus due to R. prowazekii characterized by high fever, severe headaches and generalized rashes has nowadays become a rare disease. However, the risk still exists of an outbreak of an epidemic as long as the required conditions are brought together, in particular when the population is dense and hygienic conditions are lacking.
Scrub typhus or endemic typhus, caused by R. typhi, is widespread worldwide. Rats are the carriers and their presence determines the appearance of the disease in man. The infection is characterized by headaches, myalgia and fever but, most often, the disease is benign.
Some of the infections associated with rickettsias of the eruptive fever group, and especially the Rocky Mountains spotted fever caused by R. rickettsii, can have a fatal outcome for the patient or can at the very least be accompanied by severe complications such as myocarditis, phlebitis, syndrome of meningeal irritation, encephalitis, myelitis and coma.
Scrub typhus is an acute febrile disease the causative agent of which is R. tsutsugamushi. The disease is characterized by a rise in temperature and severe headaches, which may be associated with a pneumopathy during the first week of the disease. Moreover, the disease may affect the central nervous system, with clinical manifestations such as delirium, stupor and muscle fibrillation. The death rate varies from 1 to 60% depending on the geographical regions. It is particularly high in South-East Asia, Korea, Australia, Japan and India.
At the present time, no detection technique is, at the same time, specific, sensitive and rapid enough to diagnose an infection due to bacteria of the genus Rickettsia in a biological sample. Testing for the infection is carried out essentially either by direct diagnosis, which is very awkward to carry out because it presupposes the inoculation, using biological samples, of embyronated eggs or animals; or by serological diagnosis, which is often difficult because of the lack of specificity of the techniques used or because of the delayed appearance of antibodies in the sera of patients.
The present invention relates to a technique for the diagnosis of infections caused by bacteria of the genus Rickettsia, and more particularly those caused by R. tsutsugamushi, using a genetic marker in a process of detection by hybridization of nucleic acids, combining specificity, sensitivity and speed.
More particularly, the ribosomal RNA of the bacteria is used as target. Indeed, this molecule is found in abundance in all the cells of all living organisms. Moreover, it has a specific nucleotide sequence made up of a

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