Clonal expansion of sequence type (ST-)5 and emergence of ST-7 in serogroup A meningococci, Africa

One hundred four serogroup A meningococci in our collection, isolated in Af rica from 1988 to 1999, were characterized by multilocus sequence typing (M LST). Our results and data from the Internet indicate that sequence type 5 (ST-5) strains were responsible for most of African outbreaks and sporadic cases during this period. In 1995, a new clone, characterized by ST-7 seque nce, emerged and was responsible for severe outbreaks in Chad (1998) and Su dan (1999). MLST and epidemiologic data indicate that ST-5 and ST-7 represe nt two virulent clones. These two STs, which belong to subgroup III, differ only in the pgm locus: allele pgm3 is characteristic for ST-5 and allele p gm19 for ST-7. Subgroup III strains were responsible for two pandemics in t he 1960s and 1980s. Our data show that the third subgroup III pandemic has now reached Africa.