Emergence of New Virulent Neisseria

there have been variations in the incidence of invasive meningococcal infection due to serogroup C isolates. Infection peaks were observed in 1992 and 2003 that involved isolates of phenotypes C:2a:P1.5,2 and/or C:2a:P1.5, which belong to the sequence type 11 (ST-11) clonal complex. We report an emergence of isolates belonging to the ST-11 clonal complex since 2003. These isolates displayed a new pheno-type, C:2a:P1.7,1, caused infections that occurred as clusters, and were associated with increased infection severity and high virulence in mice. These isolates may be responsible for a peak in the incidence of serogroup C meningococcal in-fection in France, for which there is no routine vaccination to date. Invasive meningococcal infections are a major public health concern because of the threat of outbreaks and epidemics. Con-jugate vaccines against Neisseria meningitidis serogroup C have been introduced in routine vaccination procedures in several countries [1]. By contrast, in France, recommendations are for targeted vaccinations alone; they are given to patients who have come into contact with infected individuals and for the control of serogroup C outbreaks [2]. The latter strategy is based on epidemiological and bacteriological surveillance data to detect outbreaks and to tailor vaccination procedures for the exposed population. Indeed, horizontal DNA exchange among menin