Australian Meningococcal Surveillance Programme Annual Report, 2024

In Australia, both probable and laboratory-confirmed cases of invasive meningococcal disease (IMD) are reported to the National Notifiable Diseases Surveillance System (NNDSS). When compared to 2023, the number of IMD notifications in 2024 decreased by 5% to 136. IMD was confirmed by laboratory testing in 136/136 (100%) of 2024 IMD cases, with 63% (86/136) diagnosed by bacterial culture and 37% (50/136) by nucleic acid amplification testing. The serogroup was determined for 96% of laboratory-confirmed cases (130/136): serogroup B (MenB) accounted for 84% of infections (109/130); MenY for 14% (18/130); MenW for 1.5% (2/130) and MenC for 0.8% (1/130). Finetyping was available on 71% of the cases for which the serogroup was determined (92/130). In MenB isolates, 21 porA types were detected, the most prevalent of which were P1.7-2,4 (38%; 29/76) and P1.7,16-26 (11%; 8/76). In MenY infections, 6 porA types were detected, with P1.5-1,10-1 the dominant porA type (60%; 9/15); where typed, this was of multilocus sequence type MLST (ST) 1655 and from clonal complex 23 (8/9). One of the two MenW isolates in 2024 was finetyped and identified as porA type P1.5,2, MLST (ST) 11 and belonging to the clonal complex 11, the hypervirulent strain reported in outbreaks in Australia and overseas. The MenC isolate was not typed. Peaks of IMD occurred in children aged less than 5 years, and in those aged 15-24 years, accounting for 20% (27/136) and 28% (38/136) of laboratory-confirmed cases respectively. In children aged under 5 years, 92% (24/26) of IMD was MenB; in those aged 15-24 years, 94% (33/35) of IMD was MenB, with serogroup not determined for one case in those aged < 5 years and three cases aged 15-24 years. IMD was reported in all age groups: < 5 years (20%; 27/136); 5-9 years (6%; 8/136); 10-14 years (5%; 7/136); 15-24 years (28%; 38/136); 25-44 years (12%; 16/136); 45-64 years (18%; 25/136); and in those aged 65 years and older (11%; 15/136). Whilst MenB predominated in all age groups, the majority of MenY IMD cases were reported in adults aged 45 years and older (14/18; 78%). All cultured IMD isolates (n = 86) had antimicrobial susceptibility testing performed with ceftriaxone and penicillin. Minimum inhibitory concentration (MIC) values were reported using Clinical Laboratory Standards Institute (CLSI) interpretative criteria: 7% (6/86) were defined as penicillin resistant (MIC value, ≥ 0.5mg/L); 60% (52/86) had intermediate susceptibility to penicillin (MIC values, 0.125 and 0.25 mg/L); and 33% (28/86) were susceptible to penicillin (MIC values, ≤ 0.064 mg/L). All isolates tested susceptible to ceftriaxone, ciprofloxacin and rifampicin.