Australian Meningococcal Surveillance Programme annual report, 2016.

Area of Science:

• Microbiology
• Epidemiology
• Public Health

Background:

• Invasive meningococcal disease (IMD) is a significant public health concern in Australia.
• Surveillance of IMD is crucial for understanding disease trends and informing public health interventions.

Observation:

• In 2016, Australia reported the highest number of laboratory-confirmed IMD cases since 2008, with 252 cases notified.
• Serogroup B cases decreased to their lowest proportion (37%) since 1997, while serogroup W (44%) and Y (16%) infections reached record highs.
• Molecular typing revealed that a majority of serogroup W strains were the hypervirulent P1.5,2/ST-11 type, consistent with global strains.

Findings:

• The primary age peak for IMD shifted to adults aged 45 years and older, with secondary peaks in children under 5 and adolescents aged 15-19.
• Serogroup B predominated in younger age groups (<1 year, 20-24 years), while serogroup W was more prevalent in older adults (≥45 years).
• Antimicrobial susceptibility testing showed 6% of isolates resistant to penicillin, with 90% exhibiting decreased susceptibility. One serogroup W isolate had elevated ceftriaxone MIC.

Implications:

• The changing serogroup distribution and emergence of specific hypervirulent strains necessitate ongoing surveillance and potential vaccine strategy adjustments.
• Increased antimicrobial resistance, particularly to penicillin, highlights the need for careful treatment selection and monitoring.
• Understanding age-specific serogroup prevalence is vital for targeted public health campaigns and vaccination efforts.