Statistical comparison of the genetic sequence type diversity of invasive Neisseria meningitidis isolates in northern Spain (1997–2008)

Abstract

A secondary effect derived from the mass vaccination campaigns against meningococcal disease could be the increase in the genetic sequence type variability of the Neisseria meningitidis. The study and measurement of diversity (or/and richness) is an old problem from Ecology. However, although there exist a huge number of diversity indices, they often do not have satisfactory statistical properties and their use in inference is limited or null. In this paper, the ratio of the number of different observed species ( S) to the number of observed individuals ( d N = S/ N) is analyzed from both non-parametric and parametric approaches. The two methodologies are applied to the problem to know whether the genetic diversity of the invasive Neisseria meningitidis is equal or not along the last twelve years (1997–2008) in a region of northern Spain (Basque Country) where two mass immunization campaigns have been carried out during this period.