Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

A possible ancient origin for tuberculoses in Casablanca

23.11.2004


Each year tuberculosis kills about three million people in the world. In particular it is responsible for the death of more than one-third of HIV- infected people, who prove particularly susceptible owing to a decline in immune defences. The agent responsible is a bacterium of the species Mycobacterium tuberculosis, also termed Koch’s bacillus, after the scientist who discovered it in 1882.



Molecular epidemiology has proved valuable for understanding the transmission and control of tuberculosis, thanks to the development of different methods of characterization of the M. tuberculosis genome. However, little genetic data is currently available in the countries of the South, where this disease is often a major public health problem. In Morocco, tuberculosis incidence is still high, with about 30 000 new cases are recorded each year, in spite of a level of HIV infection that remains of quite low concern and the application since 1991 of a WHO strategy called DOTS (2). Researchers from the IRD and their scientific partners (1) studied the genetic diversity and structure of a Moroccan population consisting of 150 strains of the species M. tuberculosis. These strains come from 150 pulmonary tuberculosis infected subjects living in Casablanca, the country’s economic capital, which on its own accounts for one-fifth of all tuberculosis cases declared in Morocco.

Two independent and complementary molecular genotyping techniques were applied to the specimens collected. The first used generalist genetic markers which allow analysis of the genetic diversity of the population considered, but also comparison of the genetic diversity of the pathogenic species M. tuberculosis with that of other microorganisms. The second, which is the most recent technique used for characterizing the M. tuberculosis genome, calls on specific markers of this mycobacterium, adapted to the identification of the different strains isolated.


The statistical analyses performed on the basis of data obtained concerning the population studied shows that it has a clonal structure: its constituent strains behave and evolve overall like natural clones that are stable with time.

Moreover, analysis of the genetic profiles of the different strains revealed a large genetic diversity in the population (3). This result was unexpected, because the populations of M. tuberculosis coming from high-incidence countries, as in Morocco, generally show a low degree of polymorphism. The polymorphism that did occur was seen between the strains of one and the same district of the city of Casablanca, between strains collected the same year and often between those resulting from the same infected family. The population studied consequently consisted of many circulating clones.

The results taken overall suggest that there is an ancient origin of tuberculosis in Casablanca. No one genetic profile was numerically dominant. Therefore transmission of the disease would be effected by reactivation of pre-existing, latent, strains rather than by recent transmissions of novel strains. The fact that several genetically different strains can affect the members of a single family shows that contamination, in this context of high incidence, can also be exogenous, the disease being contracted outside the family home. Important pieces of information on the biological, clinical and epidemiological behaviour of this mycobacterium, especially in terms of identification and treatment of different sources of contamination, have thus been contributed.

No genetic study had previously been conducted in Morocco on M. tuberculosis populations. The work performed on the sample collected at Casablanca therefore provided the first indices for understanding tuberculosis transmission in this area. Such molecular epidemiology investigations, conducted in other towns and villages of Morocco, and in other countries where the disease is endemic, favour an overall approach to the transmission dynamics of tuberculosis. This is vital if effective control measures of this disease are to be deployed.

Marie Guillaume – DIC

(1) The joint CNRS-IRD research unit Génétique et Evolution des Maladies Infectieuses (Genetics and Evolution of Infectious Diseases) has worked in tandem with the INSERM Laboratory of Molecular Mechanisms of Bacterial Pathogenesis at the Lille Pasteur Institute. Sample collection and the epidemiological survey were conducted in conjunction with the Mycobacteria Department of the Morocco Pasteur Institute at Casablanca.

(2) DOTS: Directly observed Treatment Short-course. This strategy for tuberculosis control was implemented in Morocco in 1991, with the following main objectives: application of the standard short chemotherapy course (6 months) for all new microscopically positive cases of pulmonary tuberculosis; treatment of all the other forms of tuberculosis once the diagnosis established; maintenance of vaccination cover using BCG at over 90 % in newborns. These different objectives involve the permanent commitment of government authorities in tuberculosis control and the necessity for regular, consistent supply of high-quality medicines.

(3) Moreover, this diversity appears highly significant when compared with that of other species of microorganism (bacteria, yeasts, protozoans) that evolve on the same clonal model. M. tuberculosis has a greater genetic diversity than the 4 species of Leishmania tested (average values are 0.48 as against 0.14; 0.07; 0.19 and 0.14). The value obtained for M. tuberculosis (0.48) is close to that of Saccharomyces cerevisiae (0.42) and Candida albicans (0.51).

Marie Guillaume | alfa
Further information:
http://www.ird.fr

More articles from Health and Medicine:

nachricht Using fragment-based approaches to discover new antibiotics
21.06.2018 | SLAS (Society for Laboratory Automation and Screening)

nachricht Scientists learn more about how gene linked to autism affects brain
19.06.2018 | Cincinnati Children's Hospital Medical Center

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Temperature-controlled fiber-optic light source with liquid core

In a recent publication in the renowned journal Optica, scientists of Leibniz-Institute of Photonic Technology (Leibniz IPHT) in Jena showed that they can accurately control the optical properties of liquid-core fiber lasers and therefore their spectral band width by temperature and pressure tuning.

Already last year, the researchers provided experimental proof of a new dynamic of hybrid solitons– temporally and spectrally stationary light waves resulting...

Im Focus: Overdosing on Calcium

Nano crystals impact stem cell fate during bone formation

Scientists from the University of Freiburg and the University of Basel identified a master regulator for bone regeneration. Prasad Shastri, Professor of...

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

Graphene assembled film shows higher thermal conductivity than graphite film

22.06.2018 | Materials Sciences

Fast rising bedrock below West Antarctica reveals an extremely fluid Earth mantle

22.06.2018 | Earth Sciences

Zebrafish's near 360 degree UV-vision knocks stripes off Google Street View

22.06.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>