Original Papers

Laboratory surveillance of invasive pneumococcal disease in New South Wales, Australia, before and after introduction of 7-valent conjugate vaccine: reduced disease, but not antibiotic resistance rates

S. OFTADEH^a1 c1, H. F. GIDDING^a1a2 and G. L. GILBERT^a1a3

^a1 Centre for Infectious Diseases and Microbiology – Public Health, Westmead Hospital, Westmead, NSW, Australia

^a2 School of Public Health and Community Medicine, University of New South Wales, Sydney, Australia

^a3 Sydney Institute for Emerging Infections and Biosecurity, University of Sydney, NSW, Australia

SUMMARY

We compared serotype distributions of Streptococcus pneumoniae isolates from patients aged <5 and ≥5 years with invasive pneumococcal disease in New South Wales, Australia, and antibiotic susceptibilities of isolates from the <5 years age group only, before (2002–2004) and after (2005–2009) introduction of the 7-valent pneumococcal conjugate vaccine (PCV7). Overall, there were significant decreases in the mean annual number of referred isolates (770 vs. 515) and the proportion belonging to PCV7 serotypes (74% vs. 38%), but non-PCV7 serotypes, particularly 19A, increased (5% vs. 18%). All changes were more marked in the <5 years age group. Susceptibility testing of isolates from the <5 years age group showed variation in resistance between serotypes, but significant overall increases in penicillin non-susceptibility (23% vs. 31%), ceftriaxone resistance (2% vs. 12%) and multidrug resistance (4% vs. 7%) rates; erythromycin resistance fell (32% vs. 25%). Continued surveillance is needed to monitor changes following the introduction of 13-valent PCV in 2012.

(Received June 11 2012)

(Revised August 03 2012)

(Accepted August 29 2012)

Key words

• Antibiotic susceptibility;
• broth microdilution;
• serotype distribution;
• 7-valent pneumococcal conjugate vaccine;
• Streptococcus pneumoniae

Correspondence:

^c1 Author for correspondence: Dr S. Oftadeh, Centre for Infectious Diseases and Microbiology – Public Health (CIDM), Institute of Clinical Pathology and Medical Research (ICPMR), Westmead Hospital, Darcy Road, Westmead, New South Wales, 2145 Australia. (Email: shahin.oftadeh@swahs.health.nsw.gov.au)