Annual report of the Australian Meningococcal Surveillance Programme, 2003

This tenth report by the National Neisseria Network, a nation-wide collaborative laboratory program, describes 494 laboratory-confirmed cases of meningococcal disease in Australia, diagnosed in 2003. The phenotypes (serogroup, serotype and serosubtype) and antibiotic susceptibility of 303 isolates of Neisseria meningitidis from invasive cases of meningococcal disease were determined, and an additional 191 cases were confirmed by non-culture-based methods. The age distribution of invasive meningococcal disease showed a typical primary peak in those aged four years or less which was predominantly serogroup B meningococci. A secondary peak in adolescents and young adults contained a larger proportion of serogroup C infections. Nationally, the majority of isolates were serogroup B (183 isolates, 60.4%) or serogroup C (102 isolates, 33.6%) meningococci. The number of serogroup C isolates in Victoria decreased from 72 in 2002 to 33 in 2003 and in Tasmania the number of serogroup C isolates decreased from 14 to five. Smaller decreases in serogroup C isolate numbers were recorded in most other jurisdictions but the number increased in the Australian Capital Territory from four to seven isolates. Serogroup B isolate numbers also decreased nationally but by a smaller amount. However in South Australia serogroup B infections more than doubled, and there were also increases in the Northern Territory and Australian Capital Territory. The serogroup C phenotype C:2a:P1.4 remained prominent in Victoria but elsewhere in Australia it was detected only in low numbers. 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 from the Australian Capital Territory was penicillin resistant at 1 mg/L and two, one each from South and Western Australia were rifampicin resistant.