Annual report of the Australian Meningococcal Surveillance Programme, 2006.

Abstract

In 2006 there were 271 laboratory-confirmed cases of invasive meningococcal disease analysed by the National Neisseria Network, a nationwide network of reference laboratories. The phenotypes (serogroup, serotype and serosubtype) and antibiotic susceptibility of 166 isolates of Neisseria meningitidis from invasive cases of meningococcal disease were determined and an additional 105 cases were confirmed by non-culture-based methods. Nationally, 217 (80%) confirmed cases were infected with serogroup B and 26 (9.6%) with serogroup C meningococci. The total number of confirmed cases was 74 (21%) fewer than the 345 cases identified in 2005. Numbers of cases decreased in all jurisdictions except Queensland. The age group showing the greatest decrease in numbers (by about one-third) was in those aged 25 years or more. A typical primary disease peak was observed in those aged 4 years or less with a lower secondary peak in adolescents and young adults. Serogroup B cases were 93% of all cases in those aged 4 years or less and 77% in those aged 15-24 years. The proportion of invasive disease represented by serogroup C disease was highest in the 20-24 years and 25-44 years age groups. The common phenotypes circulating in Australia were B:15:P1.7, B:4:P1.4, C:2a:P1.4 and C:2a:P1.5, but again with significant jurisdictional differences. No evidence of meningococcal capsular 'switching' was detected. About two thirds of all isolates showed decreased susceptibility to the penicillin group of antibiotics (MIC 0.06-0.5 mg/L). All isolates remained susceptible to rifampicin and ciprofloxacin.