Annual report of the Australian Meningococcal Surveillance Programme, 2004

This report by the National Neisseria Network, a nationwide collaborative laboratory programme, describes 361 laboratory-confirmed cases of meningococcal disease diagnosed in Australia in 2004. The phenotypes (serogroup, serotype and serosubtype) and antibiotic susceptibility of 245 isolates of Neisseria meningitidis from invasive cases of meningococcal disease were determined and an additional 116 cases were confirmed by non-culture based methods. Nationally, the majority of cases were serogroup B (243 isolates, 68%) or serogroup C (71 isolates, 20%) meningococci. The total number of cases was 133 fewer than the 494 cases identified in 2003 and the number of confirmed cases decreased in all jurisdictions except Western Australia where the total was unchanged. There was a 15 per cent decrease in serogroup B infections, but a greater (45%), fall in the number of serogroup C cases. The age distribution of meningococcal disease showed a typical primary peak in those aged four years or less with a secondary peak in adolescents and young adults. Serogroup B cases were 88 per cent of all cases in those aged four years or less and 63 per cent in those aged 15-24 years age range. The proportion of all invasive disease represented by serogroup C disease was highest in the 15-24 years and older age groups. The common phenotypes circulating in Australia were B:4:P1.4 and C:2a:P1.4. However, significant jurisdictional differences in the serogroup and phenotypic distribution of meningococci was again evident and considerable heterogeneity of subtypes was noted. No evidence of sustained transmission of meningococci undergoing capsular 'switching' or genetic recombination was detected. About two thirds of all isolates showed decreased susceptibility to the penicillin group of antibiotics (MIC 0.06 to 0.5 mg/L). A single isolate was penicillin resistant at 1 mg/L.