High prevalence of Neisseria meningitidis hypervirulent lineages and emergence of W135:P1.5,2:ST-11 clone in Southern Brazil.

Objectives: The aim of this study was to characterize Neisseria meningitidis strains causing invasive disease in Rio Grande do Sul (RS), during 2003-2005, monitoring the occurrence of hypervirulent lineages, as well as to determine the diversity of PorA VR types for the corresponding isolates and clinical specimens.

Methods: Isolates and clinical specimens were characterized by MLST and PorA VR typing.

Results: This study demonstrated high prevalence of some hypervirulent lineages and emergence of new ones, including the emergence of lineages W135:P1.5,2:ST-11 complex, and C:P1.22,14-6:ST-103 complex. These lineages are probably responsible for the increasing incidence of serogroups C and W135, despite the overall decrease in serogroup B cases during the period. The most prevalent complex was serogroup B ST-32/ET-5 complex. The most prevalent PorA types found for serogroup B were P1.19,15, P1.7,16, and P1.18-1,3, representing a different distribution of PorA types compared to other states of Brazil.

Conclusions: This study highlights the importance of monitoring each population, even within the same country. The different distribution of PorA VR types in RS has implications in vaccine design and efficacy. Detailed and accurate meningococcal characterization is an important element in studies of meningococcal epidemiology, population biology, and evolution and provides information for the design of control strategies.