Australian Meningococcal Surveillance Programme annual report, 2016

In 2016, there were 243 laboratory-confirmed cases of invasive meningococcal disease analysed by the Australian National Neisseria Network. This number was the highest number of laboratory confirmed cases since 2008. Probable and laboratory confirmed invasive meningococcal disease (IMD) are notifiable in Australia, and there were 252 IMD cases notified to the National Notifiable Diseases Surveillance System in 2016, the highest number reported since 2010. Meningococcal serogrouping was able to be determined for 98% (237/243) of laboratory confirmed IMD cases. Serogroup B infections accounted for 87 cases (37%), the lowest number and proportion reported since inception of the Australian Meningococcal Surveillance Programme (AMSP) in 1997. In contrast, the number and proportion of serogroup W infections (44%, 107 cases) in 2016 was the highest since the AMSP began. In addition, the number and proportion of serogroup Y infections (16%, 40 cases) was also the highest recorded by the AMSP. Molecular typing results were available for 225 of the 243 IMD cases. Of the serogroup W IMD strains that were able to be genotyped, 92% (97/105) have the PorA antigen encoding gene type P1.5,2 and of these, 72% (70/97) were sequence type 11, the same type as the hypervirulent serogroup W strain that has been circulating in the UK and South America since 2009. The primary IMD age peak was observed in adults aged 45 years or more, whilst secondary disease peaks were observed in those aged less than 5 years, and in adolescents aged 15-19 years. Serogroup B infections predominated in the age groups less than 1 year and 20-24 years, whereas serogroup W infections predominated in those aged 45 years or more. For all other age groups, distribution of serogroup B and W infections was roughly equal. Of the IMD isolates tested for antimicrobial susceptibility, 6% (11/189) were resistant to penicillin, and decreased susceptibility to penicillin was observed in a further 90% (170/189) of isolates. One Men W isolate demonstrated an elevated minimum inhibitory concentration (MIC) to ceftriaxone (0.125mg/L), the highest reported in Australia. All isolates tested were susceptible to rifampicin and ciprofloxacin.