Annual report of the Australian Meningococcal Surveillance Programme, 2001

Since 1994, The National Neisseria Network has examined and analysed isolates of Neisseria meningitidis from cases of invasive meningococcal disease in Australia by means of a collaborative laboratory program. The phenotypes (serogroup, serotype and serosubtype) and antibiotic susceptibility of 338 isolates of N. meningitidis from invasive cases of meningococcal disease were determined in 2001. Most disease was caused by serogroup B (206 isolates, 61%) or serogroup C (122 isolates, 36%) meningococci. However, there was considerable diversity in the phenotypes circulating in the different states and territories. Serogroup B strains predominated in all jurisdictions except Victoria and Tasmania and were isolated from sporadic cases of invasive disease. Serogroup B phenotypes were generally disparate with phenotype B:4:P1.4 being the most common and phenotype B:15:P1.7 was also widely distributed. Infections with a novel phenotype that was first noted in 1999, C:2a:P1.4(7), were again common in Victoria, especially in adolescents and adults, but were infrequently seen elsewhere in Australia. In Tasmania, a different phenotype, C:2a:P1.5,2 accounted for 11 of 16 isolates, again predominantly in infections of young adults. The number of isolates in Queensland increased to 78 from 43 in 2000 and was due to more strains of both serogroup B and serogroup C meningococci. About two-thirds of all isolates showed decreased susceptibility to the penicillin group of antibiotics (MIC 0.06 to 0.5 mg/L). All isolates tested were susceptible to third generation cephalosporins. From 1999, reports have also included diagnoses made by non-culture based methods in these analyses. Data relating to 135 laboratory-confirmed but culture negative cases supplemented information on culture-confirmed cases in this report.