Resumen:
It has been described that the uptake of pneumococcus involved
clathrin coated-vesicles, and bacteria proceed into vacuoles
decorated by Rab5 and Rab7, the classical route to the lysosome.
However, there is no data about the existence of a specific
pneumococcal containing-vacuole and the intracellular life of this
pathogen.
Using an in vitro infection model, we observed a decrease in the
number of intracellular bacteria in the first hours, although it
remains alive in macrophages and pneumocytes for at least 5 hours.
By immunofluorescence microscopy, long bacterial chains were
observed intracellularly. In macrophages, inhibition of lysosomal
acidification by chloroquine increased bacterial clearance,
suggesting that bacterial survival mechanism depends on
lysosomal pH. On the other hand, we focused our study in bacterial
mechanisms that would allow pneumococcus to survive inside
cells, for example, signal transduction systems. We carried out
survival assays using two-component systems mutants, and we
found that the comE mutant evaded bacterial clearance and
replicates inside the pneumocytes. These results suggested that
pneumococcus was able to survive within macrophages and
pneumocytes for several hours, and that its survival mechanism
depends on lysosomal acidification. In addition, we showed that
ComE is involved in controlling survival/death balance of
pneumococcus inside cells