Epidemiology of meningococcal disease in southern Brazil from 1995 to 2003, and molecular characterization of Neisseria meningitidis using multilocus sequence typing

OBJECTIVE To describe the epidemiology of meningococcal disease (MD) in southern Brazil. METHODS Retrospective cohort study among 2215 MD cases reported from 1995 to 2003 in Rio Grande do Sul (RS) State. RESULTS The overall incidence fell by 50%; the case-fatality rate during this period was 22%. Even so, the incidence of MD remained high after the epidemic period ended in 1999. Together, the age groups of 1-4 years and infants accounted for 54.1% of reported cases with incidences of 11.3/100 000 and 31.3/100 000, respectively; 69.8% of cases were caused by Neisseria ineningitidis serogroup B, which increased significantly. There was a significant decrease in serogroup C cases in the whole period. The phenotypes B:4,7:PI.19,15, B:15:P1.7,16 and B:NT:P1.3 caused almost 50% of all serotyped cases. Fifty-six isolates obtained from RS patients during the first non-epidemic year 2000 plus 20 isolates from other southern Brazilian states (Santa Catarina and Paran), Denmark and France were typed by multilocus sequence typing. Twenty sequence types (STs) were identified, eight of them found only in RS. ST-33 (27%) and ST-259 (18%) were the most frequent; both belong to the ST-32/ET-5 complex. ST-259 cases showed a trend towards higher risk of fatal outcome. ST-259 isolates were not detected among geographic controls or in other studies in Brazil. CONCLUSION Our data suggest that ST-33 and ST-259 clones and the emergence of the ST-103 isolates contributed to the continued high incidence of MD in RS.