Meningococcal serogroup Y lpxL1 variants from South Africa are associated with clonal complex 23 among young adults.

ABSTRACT

OBJECTIVES: To determine the genotypes of serogroup Y meningococcus (MenY), and to determine the prevalence of and identify factors associated with MenY lpxL1 variants. METHODS: Isolates, collected from 2003 to 2007 through national surveillance for invasive meningococcal disease, were characterized by multilocus sequence typing and screened for interleukin-6 induction. LpxL1 genes were sequenced from low IL-6 inducers. RESULTS: MenY represented 13% (n = 219/1702) of meningococcal disease. Clonal complex (cc) 175, ST-23/Cluster A3 (cc23), cc11 and cc167 accounted for 82% (176/214), 11% (24/214), 3% (6/214) and 3% (7/214) respectively. Low cytokine induction was evident in 15% (32/218). Cc23 isolates (24/24) had an lpxL1 mutation, while among the remaining isolates the proportion of lpxL1 variants was 4% (8/189, p < 0.001), and these were all cc175. Compared to wild type isolates, lpxL1 variants were associated with patients aged 5-14 years [unadjusted OR (95% CI) 4.3 (1.5-12)] or 15-24 years [unadjusted OR (95% CI) 9.1 (2.8-29)] compared to children <5 years; and were more likely have been isolated from CSF than blood [unadjusted OR (95% CI) 3.5 (1-11.9)]. On multivariable analysis, age remained significant [adjusted OR (95% CI), 5-14 years 4.2 (1.5-12); 15-24 years 8.9 (2.7-29)]. CONCLUSION: LpxL1 variants were associated with cc23 among young adults.