Infectious Diseases: Monitoring carriage of Streptococcus pneumoniae among Aboriginal children and adults in Western Australia

Investigators: Deborah Lehmann, Anke Hoskins, Deirdre Collins, Janice Lim, Kalpani Senasinghe, Peter Richmond in collaboration with Jacinta Bowman, Natalie Thomsen, Tom Riley, Carolien Giele, Paul Effler, Amanda Leach.

Streptococcus pneumoniae (pneumococcus) can cause middle ear infections and invasive pneumococcal disease (IPD) resulting in meningitis, pneumonia and septicaemia (blood poisoning). The Australian Aboriginal population has among the highest reported IPD rates worldwide.  The existence of over 90 known types (serotypes) of pneumococci increases the challenge of prevention. A pneumococcal conjugate vaccine (Prevenar-7™, PCV7 ) covering the 7 most common serotypes causing IPD was offered to Aboriginal children from 2001 to 2011 in a 2-4-6-month schedule.  A pneumococcal polysaccharide vaccine (Pneumovax™) covering 23 serotypes is offered to adults. While there has been a marked reduction in IPD due to the near elimination of Prevenar-7™ serotypes, in the 2000s there was an increase in IPD rates, particularly in young Aboriginal adults, due to serotypes not included in the vaccine. In light of this, Prevenar-7™ was replaced with Prevenar-13™ on 1 July 2011, which covers six additional serotypes.

Pneumococci are carried in the back of the nose of healthy as well as sick individuals and the acquisition of pneumococci is prerequisite to develop disease. Surveillance of pneumococcal carriage offers important complementary information to data on IPD since it can quickly provide a large amount of information on serotypes circulating in the population. It also gives a conservative estimate of antibiotic resistance of invasive pneumococcal strains.

This study aims to monitor the impact of different versions of PCV on pneumococcal carriage by collecting pernasal swabs opportunistically from Aboriginal adults and children in urban, rural and remote areas of Western Australia. We also collect ear swabs from children with middle ear discharge and data on vaccination status of children in the study.

Other study aims include:

  1. Describing the prevalence of upper respiratory tract (URT) carriage of other pathogens identified on primary culture, in particular non-typeable Haemophilus influenzae and Moraxella catarrhalis which cause otitis media
  2. Comparing the distribution of pneumococcal serotypes in the URT with those causing IPD in Aboriginal adults and children annually
  3. Monitoring antibiotic resistance pattern of pneumococci
  4. Storing pernasal swabs for detection of viruses by PCR to describe the prevalence of respiratory viruses and
  5. Investigating viral-bacterial interactions in the URT.

To date we have collected ~2780 pernasal swabs and 50 swabs of discharge from the middle ear.
Pneumococcal carriage rates dropped slightly after the introduction of Prevenar-13™  but remain high in young children, being highest in the 6-23month age group (~70- 80%).  More than 60% of children <6 months of age carried pneumococci. .

In children under 5 years of age nontypeable Haemophilus influenzae and Moraxella catarrhalis were each isolated from 63% of pernasal swabs. In people aged ≥5 years 22% grew nontypeable Haemophilus influenzae and 27% grew Moraxella catarrhalis. Since 2008 forty five different pneumococcal serotypes were identified in 1123 pneumococcal positive swabs. Currently, the most common pneumococcal serotypes in children <5 years of age are 19F, 6C and 16F while 19F, 10A and 15B are most common in older children and adults. It is noteworthy that carriage of 19F remains common despite its inclusion in both PCVs. There has been some reduction in carriage of serotypes included Prevenar-13™ since its introduction.

Surveillance of pneumococcal carriage is ongoing.
A paper describing nasopharyngeal carriage in the WA Aboriginal population was published in 2013 and a paper investigating risk factors for pneumococcal carriage is in draft form.

Lay summary
The pneumococcus is a bacterium that can cause serious illness and is a leading cause of pneumonia, meningitis, septicaemia (infection of the blood), and otitis media. A vaccine (Prevenar) worked well in reducing disease and in 2011 additional serotypes were included to address the change in serotypes causing disease. We want to find out which of the more than 90 different serotypes of pneumococci are carried in the noses of Aboriginal people in WA and monitor changes following introduction of PCVs. The study involves travelling around WA and taking nose swabs from healthy people and then looking at pneumococcal serotypes and other viruses or bacteria they are carrying. We also test for antibiotic resistance. Data from healthy volunteers is compared with data collected from people who developed pneumococcal disease in WA. By doing this study, we can monitor the changes in the serotypes circulating in the community and thereby inform future vaccine development and monitor effectiveness of vaccines and antibiotic treatment.

By monitoring pneumococcal carriage we are able to detect the emergence of particular serotypes that have the potential to cause IPD. Evaluating such data might lead to the development of appropriate vaccines.
Through our extensive field activities we have numerous opportunities to discuss concerns regarding pneumococcal disease, the vaccine and the value of surveillance with Aboriginal communities and families as well as health service providers. This includes reducing risk factors we identified such as smoking and overcrowding and the role of hygiene.

Funders of the project: Western Australian Department of Health through the Collaboration for Applied Research and Evaluation (CARE) and NHMRC Project Grant #545232 (a collaboration with the Menzies School of Health Research).

Team Members

Deborah Lehman

Anke Hoskins

Deirdre Collins

Janice Lim

Kalpani Senasinghe

Peter Richmond

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