Annual report of the Australian Meningococcal Surveillance Programme, 1997.

The National Neisseria Network (NNN) 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 343 isolates of Neisseria meningitidis from invasive cases of meningococcal disease were determined in 1997. Ninety six percent of the invasive isolates were serogroup B or C. Serogroup B strains predominated in all States and Territories and were isolated from sporadic cases of invasive disease. Phenotypes B:4:P1.4 and B:15:P1.7 were prominent. Serogroup C isolates were most often encountered in New South Wales, especially in adolescents and young adults, and in that State were nearly as numerous as serogroup B strains. C:2a:P1.5 was the most frequently encountered phenotype and C:2b:P1.2 strains were also distributed widely. A number of clusters of cases of serogroup C disease were noted, mainly with phenotype C:2a:P1.5. 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 and one was chloramphenicol resistant.