Staphylococcus aureus ST228 and ST239 as models for expression studies
of diverse markers during osteoblast infection and persistence
Abstract
The ability of S. aureus to infect bone and osteoblasts is correlated to
its incredible virulence armamentarium that can mediate the
invasion/internalization process, cytotoxicity, membrane damage and
intracellular persistence. We comparatively analyzed the interaction,
persistence and modulation of expression of selected genes as well as
cell viability in an ex-vivo model using human MG-63 osteoblasts of two
previously studied and well-characterized S. aureus clinical strains
belonging to ST239-SCCmecIII-t037 and ST228-SCCmecI-t041 clones at 3h
and 24h post-infection (p.i). ATCC12598 was used as a control strain.
Using Imaging Flow Cytometry analysis, we found that strains differently
invaded osteoblasts after 3h and 24h: ATCC12598 internalized in 70% and
50% of cells, ST239-SCCmecIII in 50% and 45% and ST228-SCCmecI in
30% and 20%, respectively. ST239-III, during the infection period,
exerted a significative cytotoxic activity due to the over-expression of
hla and psmA and the increased expression of the genes involved in
adhesion, probably due to the release and re-entry of bacteria inside
MG-63 at 24h p.i. The lower invasiveness of ST228-I was also correlated
with the non-cytotoxic activity inside osteoblasts. This clone was not
able to activate a sufficient cellular reaction and succumbed in-side
the MG-63 cells.