Annual report of the Australian Meningococcal Surveillance Programme, 1999

The National Neisseria Network has undertaken meningococcal isolate surveillance by means of a collaborative laboratory based initiative since 1994. The phenotype (serogroup, serotype and serosubtype) and antibiotic susceptibility of 368 isolates of Neisseria meningitidis from invasive cases of meningococcal disease were determined in 1999. Ninety percent of the invasive isolates were either serogroup B or C. Serogroup B strains predominated in all States and Territories and were isolated from sporadic cases of invasive disease. Serogroup B phenotypes were generally diverse, but in New South Wales phenotype B:4:P1.4(7) became more prominent. The number of serogroup C isolates increased significantly in Victoria and remained prominent in New South Wales, especially in adolescents and adults. Phenotype C:2a:P1.2, infrequently isolated prior to 1999, was the most frequently encountered serogroup C phenotype. A number of infections with a phenotype new to Australia, C:2a:P1.4(7), were noted in Victoria and to a lesser extent in New South Wales. Phenotype C:2a:P1.5 was less frequently encountered than in previous years. About three-quarters of all isolates showed decreased susceptibility to the penicillin group of antibiotics (MIC 0.06 to 0.5 mg/L). Three isolates showed reduced susceptibility to rifampicin. Data relating to 92 laboratory-confirmed but culture-negative cases were included in this report. Some differences in the patterns of disease were revealed when culture-based and non-culture-based data were compared.