Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1992-04-14
1997-01-28
Jones, W. Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
536 2433, 435 6, 435 912, 530350, C07H 2100, C12Q 168, C12P 1934, C07K 1400
Patent
active
055979114
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to nucleic acid fragments derived from the genome of an appropriate mycobacterium, in particular Mycobacterium tuberculosis, to their applications in the diagnosis of mycobacterial infections, and to plasmids containing the said fragments.
2. Description of the Background
Mycobacteria correspond to the Mycobacterium genus which comprises at least 54 different species.
Among them, about 10 are pathogenic or opportunistic for man or animals. Two of them, M. tuberculosis and M. Leprae are the agents for tuberculosis and leprosy respectively.
It is known that these two diseases represent a major public health problem; indeed, there are currently between 15 and 60 million people afflicted by tuberculosis worldwide and 2 to 3 million people die each year as a result of this infection. M. tuberculosis is the most common cause of mycobacterial infections in developed countries. In France, 10.sup.4 new cases of tuberculosis appear each year. Vaccination using BCG (Bacille Calmette-Gu erin, an attenuated strain of M. bovis) is far from being effective in the entire population. This efficacy ranges from about 80% in western countries such as England, to 0% in India (results of the last vaccination trial in Chingleput). Furthermore, the appearance of M. tuberculosis strains resistant to the usual anti-tuberculotics and the existence of a correlation between tuberculosis and AIDS adds to the urgency of developing a rapid method of detection and identification of mycobacteria.
For example, an epidemiological study carried out in Florida has shown that 10% of AIDS patients suffer from tuberculosis at the time of the AIDS diagnosis or 18 months before it. In these patients, tuberculosis appears in 60% of cases in a disseminated form which is therefore undetectable by conventional diagnostic tests such as pulmonary radiography or sputum analysis.
Finally, the diagnosis of tuberculosis and other related mycobacterioses is difficult to carry out for various reasons: the pulmonary diseases caused by various mycobacteria cannot be clinically, radiologically or histologically differentiated; mycobacteria are often present at low levels and when they are at levels detectable by the conventional methods used, the disease has already developed and the patients are contagious to others; furthermore, because of the very long generation time in these bacteria (24 h for M. tuberculosis compared with 20 rain for E. coli), the culture of these organisms is difficult. Thus, 6 to 8 weeks are required in order to identify the microbes and more time is required in order to obtain an antibiogram which can be used for the appropriate treatment of the patients. It is therefore essential to be able to have available a detection test which does not require the culture of microbes and which may be used directly with the pathological samples even when the microbes are present therein in low concentrations.
Several techniques are currently used clinically to identify a mycobacterial infection.
First, the direct microscopic detection of the microorganisms should be mentioned; this technique is rapid, but it does not permit identification of the mycobacterial species observed and it lacks sensitivity insofar as a large number of microorganisms must be present in the sample (>10.sup.4 /ml) in order to permit reliable detection (BATES J., CHEST, 1979, 76, (suppl.), 757-763).
The cultures, when they are positive, have a specificity close to 100% and permit the identification of the mycobacterial species isolated; however, as specified above, the growth of the mycobacteria in vitro can only be achieved in 3 to 6 weeks and when few mycobacteria are present at the infection site, repeated cultures are required in order to ensure a correct result (BATES J., 1979 and BATES J. et al., Am. Rev. Respir. Dis., 1986, 134, 415-417).
Serological techniques may prove to be advantageous under certain conditions but their use is limited by their low sensitivity and/or specificity (
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Brisson-Noel Anne
Gicquel Brigitte
Guesdon Jean-Luc
Thierry Dominique
Ullmann Agn es
Institut Pasteur
Jones W. Gary
Schreiber David
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