Australian Meningococcal Surveillance Programme annual report, 2015

In 2015, there were 174 laboratory-confirmed cases of invasive meningococcal disease analysed by the Australian National Neisseria Network. This number was higher than that reported in 2013 and 2014, which were the lowest and second-lowest totals reported, respectively, since inception of the Australian Meningococcal Surveillance Programme in 1994. Probable and laboratory confirmed invasive meningococcal disease (IMD) is notifiable in Australia. There were 182 IMD cases notified to the National Notifiable Diseases Surveillance System in 2015, again, higher than in 2013 and 2014, which were the lowest and second-lowest totals of IMD cases recorded, respectively, by this system. Meningococcal serogrouping was able to be determined for 168/174 (97%) laboratory confirmed IMD cases. Of these, 64.2% (108 cases) were serogroup B infections, the lowest reported since 2003. Further, the number and proportion of cases of serogroup C IMD, (1.2%, 2 cases), was the lowest yet reported. By contrast, in 2015 in Australia, there was a marked increase in the number and proportion of serogroup W IMD (21.4%, 36 cases), and an increase in serogroup Y IMD (13.1%, 22 cases). The number and proportion of IMD cases caused by serogroups W and Y was the highest reported since the inception of the Australian Meningococcal Surveillance Programme in 1994. Molecular typing results were available for 140 of the 174 IMD cases. Of the 31 serogroup W IMD strains that were able to be genotyped, 25/31 (81%) were sequence type (ST)-11, and have the porA antigen encoding gene type P1.5,2, the same genotype as the hypervirulent serogroup W strain of that has been circulating in the United Kingdom and South America since 2009. In 2015, the most common serogroup B porA genotype circulating in Australia was P1.7-2,4. The primary IMD age peak was observed in adults aged 45 years or more, which was the first time that this was noted by the AMSP, whilst secondary disease peaks were observed in those aged 4 years or less, and in adolescents (15-19 years). Serogroup B cases predominated in all jurisdictions and age groups, except for those aged 45 years or over where serogroups W and Y predominated. All IMD isolates tested were susceptible to ceftriaxone and ciprofloxacin. One isolate was resistant to rifampicin. Four isolates were resistant to penicillin. Decreased susceptibility to penicillin was observed in 86% of isolates.