Annual report of the Australian Meningococcal Surveillance Programme, 2011

In 2011, there were 241 laboratory-confirmed cases of invasive meningococcal disease (IMD) analysed by the National Neisseria Network, which represented 100% of cases notified to the National Notifiable Diseases Surveillance System. One hundred and twenty-five isolates of Neisseria meningitidis from invasive cases of meningococcal disease were available for which the phenotypes (serogroup, serotype and serosubtype) and/or genotype and antibiotic susceptibility were determined. An additional 116 cases were confirmed by non-culture based methods (95 by nucleic acid amplification testing (NAAT) and 21 by serology), and where possible, serotyping was determined. Nationally, 179 (83.6%) laboratory-confirmed cases, where a serogroup was determined, were infected with serogroup B; 9 (4.2%) with serogroup C; 11 (5.2%) with serogroup W135 and 15 (7%) with serogroup Y meningococci. In 2011 there was a modest increase in the number of cases of IMD notified from that reported in 2010 (214). However, with the exception of 2010, this was the lowest number of laboratory confirmed IMD cases since surveillance data were recorded. Primary and secondary disease peaks were observed in those aged 4 years or less and in adolescents (15-19 years) and young adults respectively (20-24 years). There was also a disease peak observed in those aged 45-64 years. Serogroup B cases predominated in all age groups and jurisdictions. In 2011, the most common phenotype circulating in Australia was B:4:P1.7, corresponding to the porA genotype P1.7,2-4. Serogroup C cases were again numerically low, as were serogroups W135 and Y, however there was an increase in incidence of serogroup Y cases (7 in 2010, 15 in 2011). The proportion of isolates with decreased susceptibility to the penicillin group of antibiotics minimal inhibitory concentration (MIC) (0.06 to 0.5 mg/L) was 84.6% and 1 isolate exhibited relative resistance to penicillin (MIC = 1.0 mg/L). All isolates remained susceptible to ceftriaxone and ciprofloxacin. One isolate had reduced susceptibility to rifampicin (MIC = 0.5 mg/L).