Neisseria meningitidis sequence type and risk for death, Iceland

Abstract

Invasive meningococcal infections are hyperendemic in Iceland, a relatively isolated country in the mid-Atlantic. We performed a nationwide study on all viable meningococcal strains (N = 362) from 1977 to 2004. We analyzed the association of patient's age and sex, meningococcal serogroups, and sequence types (STs) with outcomes. Overall, 59 different STs were identified, 19 of which were unique to Iceland. The most common STs were 32 (24.6%), 11 (19.9%), and 10 (10.2%). The unique ST-3492 ranked fourth (7.7%). The most common serogroups were B (56.4%), C (39.8%), and A (2.2%). Age (p < 0.001) and infection with a unique ST (p = 0.011) were independently associated with increased death rates, whereas isolation of meningococci from cerebrospinal fluid only was associated with lower death rates (p = 0.046). This study shows evolutionary trends of meningococcal isolates in a relatively isolated community and highlights an association between unique STs and poor outcome.

Figure 1

Annual number of invasive meningococcal isolates by serogroup, Iceland, 1977–2004.

Figure 2

Phylogenetic relationships of invasive meningococcal isolates in Iceland, 1977–2004. Unweighted pair-group method with arithmetic mean (UPGMA) was used to construct the tree with the Sequence Type Analysis and Recombinational Tests (START) suite of programs. Sequence types (STs) and allelic profiles are given on the right. All STs that were encountered in >3 clinical cases and all new STs are shown.