The Australasian Society of Infectious Diseases conference
The Australasian Society of Infectious Diseases (ASID) annual scientific meeting was held in Auckland from 18 – 21 March, 2015.
A wide range of topics were discussed, many of which have relevance for primary care in New Zealand, including: the impact of pneumococcal
vaccination on rates of invasive pneumococcal disease and otitis media in New Zealand; MRSA and the use of fusidic acid in New Zealand;
and a collaboration which aims to develop a vaccine against Group A Streptococcus, the bacteria that causes acute rheumatic fever.
Invasive pneumococcal disease rates have dropped following introduction of routine pneumococcal vaccination
Dr Helen Petousis-Harris from the Immunisation Advisory Centre at the University of Auckland presented data linking
falling hospitalisations from pneumococcal disease targeted by pneumococcal vaccines across all age groups with the introduction
of routine vaccinations for infants.
Prior to the introduction of the pneumococcal disease vaccine to the National Immunisation Schedule in 2007 (currently
four doses by age 15 months), annual rates of invasive pneumococcal disease were 100 per 100,000 children aged two years
and under in New Zealand.1 The financial cost of pneumococcal disease in New Zealand was estimated at $10
million per year.2
The data presented at the conference covered the period 2006 to 2013. The study is yet to be published in full, but
preliminary figures indicate that:3
- The rate of hospitalisation from invasive pneumococcal disease (meningitis or bacteraemia) in children aged six
years and under has halved
- The greatest reductions in hospitalisations from invasive pneumococcal disease were among Māori and Pacific children,
and children from low socioeconomic backgrounds, where a reduction of 70% has occurred
- There has been a decrease in hospitalisations for pneumonia in children aged six years and under, particularly Māori
and Pacific children where reductions of 41% and 37% were observed
- Herd immunity effects have been observed, with rates of hospitalisation from pneumococcal disease caused by serotypes
covered by the vaccine halved in people aged five to 64 years, and decreased by 76% in people aged 65 years
- In 2013, in children aged five years and under there was just one case of invasive pneumococcal disease caused by
a serotype covered by the PCV-7 vaccine
Surveillance data from the Institute of Environmental Science and Research (ESR), however, show that while there have
been herd immunity effects observed in people aged five years and over, with a reduction in the number of cases caused
by serotypes covered by the PCV-7 and PCV-10 vaccines, there has also been an increase in the rate of invasive pneumococcal
disease due to other serotypes of S. pneumoniae not covered by these vaccines.4 It is hoped
that the introduction of the PCV-13 vaccine in 2014 will help decrease overall rates of disease, as a substantial proportion
of cases in New Zealand are now due to serotypes covered by the PCV-13 vaccine but not previous vaccines. These serotypes
are also covered by the 23-PPV vaccine.
For further information on the pneumococcal vaccines and eligibility for funding, see the Immunisation Handbook, 2014:
Otitis media rates have fallen following introduction of the PCV-10 pneumococcal vaccine
In addition to potentially life-threatening illnesses such as pneumococcal meningitis and bacteraemia, S. pneumoniae infections
can cause otitis media, which has the potential to result in long-term hearing problems in children, and is associated
with high rates of antibiotic use and increased healthcare costs.5 The introduction of the PCV-10 vaccine
in New Zealand in 2011 (now replaced by PCV-13) was predicted to reduce the incidence of otitis media.6 This
was thought due to the wider range of coverage against S. pneumoniae serotypes and the fact that the PCV-10
vaccine is conjugated to a protein from H. influenzae, which results in the vaccine offering some protection
against otitis media due to H. influenzae infection.
Data presented at the ASID conference indicate that:3
- A decline in hospitalisations for otitis media occurred during 2011- 2014, the period of use of the PCV-10 vaccine.
This was observed particularly in Māori children: hospitalisations and procedures for otitis media in Māori
children aged six years or under were 40% lower in 2013 compared to 2006, the year prior to routine vaccination
- During the time that both PCV-7 and PCV-10 vaccines were in use, children who received at least one dose of the
PCV-10 vaccine were less likely to be admitted to hospital with otitis media than children receiving only
the PCV-7 vaccine
A reduction in otitis media cases is likely to reduce antibiotic prescribing. Although this has not been assessed in
New Zealand, research from Finland has reported an 8% reduction in the use of antibiotics recommended for the treatment
of otitis media in the first 33 months of life for children who receive the pneumococcal vaccine.7 Although
this effect may seem modest, given the high rates of antibiotic use in children of this age (1.4 to 1.7 prescriptions
per child per year in this study), this reduction was equivalent to one less antibiotic prescription for every five children
A reduction in cases of otitis media in children, and associated antibiotic use, is welcome news not only as it represents
improved health outcomes for New Zealand children, but also because research published in 2015 confirms that antibiotic
resistance in cases of otitis media is an ongoing concern. Out of 206 samples of S. pneumoniae collected
from children undergoing grommet surgery in 2011 at Starship Children’s Health, KidzFirst (Counties Manukau District Health
Board) and Christchurch Hospital:8
- 10% showed resistance to penicillin
- Of cases resistant to penicillin, 90% showed multi-drug resistance (to three or more antibiotic classes)
- 30% were resistant to co-trimoxazole
- Approximately 20% were resistant to clindamycin, erythromycin or tetracycline
For further information on the treatment of otitis media, see:
For further information on pneumococcal vaccination, see:
Fusidic acid resistance and MRSA
Dr Deborah Williamson, from the University of Otago, Wellington, presented research showing a rise in fusidic acid resistance
in Staphylococcus aureus in New Zealand and explained how this is linked to an increase in methicillin-resistant S.
Fusidic acid resistance in S. aureus isolates from patients in hospital and community settings increased
from 17% in 1999 to 29% in 2013.9 New Zealand now has one of the highest prevalence of S. aureus resistance
to fusidic acid in the world. Genetic analyses of MRSA samples has shown that a “home grown” strain of MRSA, labelled
ST5-IV, was first identified in samples in New Zealand in 2005 but has risen to become the dominant strain of MRSA, making
up 34.7% of all MRSA clones isolated from clinical specimens in New Zealand in 2011.10 This ST5-IV strain
is almost always fusidic acid resistant, and the gene which gives this strain resistance to fusidic acid is located near
to the gene which confers methicillin resistance. Therefore, selection pressure for fusidic acid resistance in this strain
is also selecting for methicillin resistance as these genes tend to be inherited together.3
Previous research has reported that from 2005 to 2011 there was a doubling of MRSA prevalence in New Zealand from 8.6
to 18.0 cases per 100,000 people, with the highest MRSA prevalence rates in people aged 65 years or over and children
aged five years or under.10 There was no change in the rate of hospital-acquired infections, but there were
increases in the rates of community-associated MRSA and MRSA isolated in hospital within 48 hours of patient admission.
This suggests that community spread of MRSA is the main driver of the increase in MRSA prevalence during this time.
The most recent data from ESR, using S. aureus samples collected in March 2014, show that 8.9% were methicillin
resistant. Resistance to fusidic acid was found in 57.6% of methicillin resistant S. aureus isolates, as
well as 21.8% of methicillin-susceptible S. aureus isolates. Among MRSA isolates, resistance rates to erythromycin
were 25.3% and ciprofloxacin 16.1%.11
There are few clinical indications for topical fusidic acid treatment; it may be considered as a treatment for small
areas of impetigo, however, often oral antibiotic treatment is required. Topical fusidic acid may be used as part of a
S. aureus decolonisation regimen if the isolate is sensitive to fusidic acid.
Current restrictions are in place for a maximum of 15 g of fusidic acid cream or ointment per prescription.12 For
many patients this is likely to be more than necessary to complete their course of topical treatment. In order to reduce
inappropriate use, patients should be advised to see their doctor for any future skin infections and not to reinitiate
fusidic acid treatment of their own accord.
For further information on fusidic acid and MRSA, see:
Rheumatic fever vaccine development
The work of the Coalition to Advance New Vaccines for Group A Streptococcus (CANVAS) collaboration was
presented by Professor John Fraser, team leader of the New Zealand component of the collaboration. The CANVAS
collaboration is a trans-Tasman initiative to develop a vaccine against Group A Streptococcus (GAS), which is the cause
of a number of infections, such as pharyngitis, cellulitis, pneumonia and bacteraemia. Non-suppurative sequelae of GAS
infection include acute rheumatic fever, rheumatic heart disease and post-streptococcal glomerulonephritis. A reduction
in the rates of these complications is the key reason for development of this vaccine. The collaboration involves researchers
from the University of Auckland and the Telethon Kids Institute, and is affiliated to the University of Western Australia.
It is funded by both the Australian and New Zealand governments, who have committed $3.2 million to the initiative.3
The initial goals of the CANVAS project are to identify common disease strains and establish which vaccine candidates
currently under development best target these strains. Three to four vaccine candidates have been identified and work
is underway to move the best one forward into clinical trials.3
Thank you to Dr Helen Petousis-Harris and Dr Deborah Williamson for providing guidance on this article.
- Heffernan HM, Martin DR, Woodhouse RE, et al. Invasive pneumococcal disease in New Zealand 1998-2005: capsular
serotypes and antimicrobial resistance. Epidemiol Infect 2008;136:352–9.
- Milne RJ, Vander Hoorn S. Burden and cost of hospital admissions for vaccine-preventable paediatric pneumococcal
disease and non-typable Haemophilus influenzae otitis media in New Zealand. Appl Health Econ Health
- Science Media Centre. SMC BRIEFING: Superbugs and vaccines – infectious disease. 2015. Available from:
www.sciencemediacentre.co.nz/2015/03/18/superbugs-and-vaccines/ (Accessed Jun, 2015).
- Institute of Environmental Science and Research Ltd (ESR). Invasive pneumococcal disease in New Zealand, 2013.
Porirua: ESR, 2014.
- Lieberthal AS, Carroll AE, Chonmaitree T, et al. The diagnosis and management of acute otitis media. Pediatrics
- Walls T, Best E, Murdoch D, et al. Vaccination to prevent otitis media in New Zealand. N Z Med J 2011;124 (1340):6–9.
- Palmu AA, Jokinen J, Nieminen H, et al. Effect of pneumococcal Haemophilus influenzae protein D conjugate vaccine
(PHiD-CV10) on outpatient antimicrobial purchases: a double-blind, cluster randomised phase 3–4 trial.
Lancet Infect Dis 2014;14:205–12.
- Mills N, Best EJ, Murdoch D, et al. What is behind the ear drum? The microbiology of otitis media and the nasopharyngeal
flora in children in the era of pneumococcal vaccination. J Paediatr Child Health 2015;51:300–6.
- Williamson DA, Monecke S, Heffernan H, et al. High usage of topical fusidic acid and rapid clonal expansion of
fusidic acid-resistant Staphylococcus aureus: a cautionary tale. Clin Infect Dis 2014;59:1451–4.
- Williamson DA, Roberts SA, Ritchie SR, et al. Clinical and molecular epidemiology of methicillin-resistant Staphylococcus
aureus in New Zealand: rapid emergence of sequence type 5 (ST5)-SCCmec-IV as the dominant community-associated
MRSA clone. PLoS ONE 2013;8:e62020.
- Heffernan H, Bakker S, Woodhouse R, et al. Demographics, antimicrobial susceptibility and molecular epidemiology
of Staphylococcus aureus in New Zealand, 2014. Porirua: ESR, 2015.
- New Zealand Formulary (NZF). NZF v34. 2015. Available from: www.nzf.org.nz (Accessed Jun, 2015).