posted on 2010-05-21, 10:52authored bySonia Da Cruz Manco
This study focuses on the Streptococcus pneumoniae virulence factors
neuraminidases A and B, autolysin and superoxide dismutase, with the aim of
improved understanding of their roles in the pneumococcal infections.
Understanding the pathogenesis of pneumococcal infection is important because
this bacterium is one of the most common bacterial causes of human disease and
death and because of the emergence of multidrug-resistant strains and issues with
the current vaccines.
Using a murine model of bronchopneumonia it was shown that NanA and
NanB have involvement in colonisation of the upper respiratory tract and in
systemic spread. Lack of either of these proteins enhanced bacterial clearance in
the nasopharynx, lungs and blood. Furthermore, this study demonstrated distinct
roles for each of the neuraminidases, but also suggests synergistic action.
Infection data clearly show that the absence of one neuraminidase is not
compensated by the presence of the other. This study identified, for the first time,
a role for NanB in pathogenesis and in multiplication at mucosal sites.
The major S. pneumoniae autolysin LytA has been implicated in
pathogenicity by releasing virulence factors and components of the cell wall. In this
study, the avirulence of a pneumococcal autolysin-deficient mutant was confirmed.
Moreover, the results show that early after infection, LytA is crucial to
pneumococcal survival and growth, both in the upper and lower respiratory tract.
The major pneumococcal enzyme for detoxifying superoxide is MnSOD,
encoded by sodA. This study showed that absence of sodA impaired survival in
the respiratory tract, particularly early after infection, but its absence was not
lethal, suggesting that other mechanisms are involved in superoxide detoxification.