Staphylococcus aureus ST228 and ST239 as models for expression
studies of diverse markers during osteoblast infection and persistence
Dafne Bongiorno1*, Nicolò Musso2*,
Giuseppe Caruso3*, Lorenzo Mattia
Lazzaro1, Filippo Caraci3,4,
Stefania Stefani1 and Floriana
Campanile1.
1Department of Biomedical and Biotechnological
Sciences (BIOMETEC) - Medical Molecular Microbiology and Antibiotic
Resistance laboratory (MMARLab ), University of Catania, 95125
Catania, Italy;
2 Department of Biomedical and Biotechnological
Sciences (BIOMETEC), University of Catania, 95125 Catania, Italy;
3Oasi Research Institute - IRCCS, 94018 Troina (EN),
Italy;
4 Department of Drug Sciences, University of Catania,
95125 Catania, Italy;
* These authors equally contributed to the paper.
Corresponding Author:
Dafne Bongiorno
Department of Biomedical and Biotechnological Sciences (MMARL)
University of Catania
Via Santa Sofia, 97
95123 Catania, Italy
Tel: +39 095 4781238
Email: d.bongiorno@unict.it
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-SCCmec III-t037 and
ST228-SCCmec I-t041 clones at 3h and 24h post infection (p.i).
ATCC12598 was used as 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-SCCmec III in 50% and 45% and ST228-SCCmec I in 30%
and 20%, respectively. ST239-III, during the infection period, exerted
a significative cytotoxic activity due to the over-expression ofhla and psm A 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 inside the MG-63 cells.
Keywords : MRSA, ST228, ST239, osteoblast, cross-talk mechanism,
virulence toxin.