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Abstract(s)
The aim of this research was to analyze pneumococcal gene expression during
interactions with human nasal epithelial cells and comparison with other different
infection models. As the number one cause of bacterial pneumonia and one of the major
causes of mortality and morbidity, S. pneumoniae has been a target of several studies in
past years. Oggioni and colleagues (2006) studied pneumococcal gene expression
during infection in two different scenarios, bacteria in the blood and bacteria in the
tissue (as brain and lung). In this current study the target genes analyzed were nanA, ply,
comX, nox, sodA, since these were reported as up regulated in the lung (Oggioni et al.,
2006), except for ply, that was chosen because of its importance in pneumococcal
infection.
It has been reported that induction of competence system by the quorum sensing peptide
stimulates the bacteria to grow in biofilm and also increases S. pneumoniae virulence.
Based on these results, we attempted to induce biofilm formation prior to infection with
the aim to increase pneumococci virulence before adherence to nasal epithelial cells.
However, unlike Oggioni et al., (2006), our method was unsuccessful in producing
biofilm and therefore it was impossible to proceed. A further idea was to analyze
pneumococcal gene expression in apical fluid that is released and present on the surface
of human epithelial cells. It was thought that this could elucidate mechanisms of how
pneumococci overcome host defense. However, antibiotics that were used for cell
culture were detected in the apical fluid and therefore, it was not possible to continue
with this experiment since all the bacteria died within 30 minutes of exposure. For these
reasons the main aim of this study was to explore the mechanisms of pneumococcal
adherence to basal cells. Gene expression analysis was performed using three reference
conditions, S. pneumoniae in BEBM, in TSB and the non adhered pneumococci. BEBM
proved to be the best reference condition and using this we have shown that all the
genes we targeted were up regulated within 2h of exposure to basal cells, for adhered
and non adhered bacteria, except comX and sodA. NanA (neuraminidase gene) showed
the highest increase in expression levels compared to the other genes, 25,47±2,21 for
the adhered pneumococcus to patient sp282 basal cells and 23,10±0,47 for the non
adhered bacteria to patient 455 basal cells. After 6h, all genes were up regulated except
ply.
Description
Dissertação mest., Engenharia Biológica, Universidade do Algarve, 2008
Keywords
Teses Células epiteliais Genética Virologia Streptococcus pneumonial