Les méningocoques à travers le monde : marqueurs phénotypiques et moléculaires

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The first markers of meningococci were serogroup, defined by different polyosidic capsular immunospecifities (12 are described at present), and are still of great importance. Several other antigenic structures such as outer membrane proteins (OMPs) are used as markers : OMP serotypes of classes 2 and 3, OMP subtype of class 1. Serogroups, serotypes, subtypes and sometimes immunotypes (based on LPS) are associated in an antigenic formula (AF). At a world-wide level, the Electrophoretic Type (ET) defined by Multilocus Enzyme Electrophoresis (MLEE) is the most useful marker. For instance, the ET-5 and ET-37 have been described. The ET-5 was constituted primarily, but not exclusively, by strains of AF:B:15:P1.7,16 and B:4:P1.15. The ET-37 was constituted mostly by strains C:2a:P1.2,5. Two pandemics were due to Neisseria meningitidis serogroup A. They were mainly defined by MLEE. The first began in China in 1966, crossed Europe, and ended in Brazil in 1974 where it was responsible for a particularly widespread outbreak. The second pandemic, due to the same epidemic invasive strain A:4:P1.9/clone III-1 also began in China in 1983, spreading through Nepal, northern India. It was responsible for a severe oubreak in Mecca in August of 1987. It spread all around the world when the pilgrims returned to their countries. In countries with adequate health care facilities, the pandemic was stropped within two or three weeks. Unfortunately, in countries without these health care facilities, the spreading continues. For instance in Africa, specifically Niger, strains of this type continued to be isolated through the beginning of 1996. Molecular epidemiology markers like pulsotype and ribotype for instance, are able to demonstrate genetic variability between strains.