SPINCA

Aim/goal of project
To improve our understanding of their role in maintaining the high rates of pneumococcal colonisation (eg. by escape from vaccine-induced antibodies), and as a reservoir of antibiotic resistance genes.

Background
The pneumococcus is a bacterium that causes diseases such as pneumonia and middle ear infections, especially in children. All children in Australia now receive a vaccine called Prevenar which protects from disease caused by 7 types of pneumococcus. Studies have shown that the remaining types of pneumococcus not included in the vaccine will now become more prevalent (replacement types). The current proposal will look at non-encapsulated pneumococcus which is an important replacement type in Aboriginal children who have been vaccinated with Prevenar. Previously this type of pneumococcus received little attention, and little is understood about its epidemiology. Nonencapsulated pneumococci are the most common pneumococcal type colonising Indigenous children in remote communities.

Despite a lot of research we do not know a lot about how the pneumococcus survives in the human nasal passages, how it invades the body nor how it ‘hides’ itself from the immune response, particularly how it may hide from vaccines.  The pneumococcus has an outer layer (capsule) which is needed for it to cause disease. This capsule is also the main target of the immune response and vaccines.  This study shows that the pneumococcus ‘turns off’ it’s capsule which may help it to avoid being killed by the immune response. This appears to be something the pneumococcus has always been able to do, and is not caused by the vaccine.  This is an important finding because knowing how to turn off capsule may lead to discovery of new strategies to prevent the pneumococcus from causing disease.

Publication
J Clin Microbiol. 2010 Mar;48(3):831-5. Epub 2009 Dec 30.
The nonserotypeable pneumococcus: phenotypic dynamics in the era of anticapsular vaccines.
Marsh R, Smith-Vaughan H, Hare KM, Binks M, Kong F, Warning J, Gilbert GL, Morris P, Leach AJ.
Findings: It appears that most NSP identified in Australian Indigenous children are from a true nonencapsulated lineage. Few NSP represented serotypes in PCV7 that suppress capsular expression. High rates of carriage and penicillin resistance and the occasional presence of capsule genes suggest a role for NSP in the maintenance and survival of capsulated pneumococci. To avoid the inflation of pneumococcal carriage and antibiotic resistance rates, in clinical trials, we recommend separate reporting of rates of capsular strains and NSP and the exclusion of data for NSP from primary analyses.
Links/newsletters http://www.ncbi.nlm.nih.gov/pubmed/20042626
Marsh R, Smith-Vaughan H, Hare KM, Binks M, Kong F, Warning J, et al. The nonserotypeable pneumococcus: phenotypic dynamics in the era of anticapsular vaccines. J Clin Microbiol 2010 Mar;48(3):831-5.