Conclusion
We found that the ST239-III clone was able to infect, at 3h p.i., 50% of MG-63 human osteoblasts and these rates stably persisted at 24h p.i.; during the infection peri-od it exerted an extremely significative cytotoxic activity against osteoblasts, due to the over- expression ofhla and psm A, as demonstrated by a remarkable decrease in the cellular metabolic status. The increase of hla and psmA has as a consequence the increased of expression of the genes involved in adhesion (bbp ), probably due to the release and re-entry of bacteria inside MG-63 at 24h p.i. Our results lead us to conclude that the ST239 clone is more prone to persistent infections.
On the contrary, ST228-I was found to be less able to internalize (30%), with respect to the control strain and ST239-III, after 3h p.i. and to persist (20%) at 24h p.i., and this lower in-vasiveness was also correlated with the non-cytotoxic activity inside osteoblasts. This is probably due to the presence of the pls gene into SCCmec I, that is involved in the failure to adhere to the cell surface. This clone is not able to activate a sufficient cellular reaction, and succumbs inside the MG-63 cells.
Author contributions: Dafne Bongiorno : Conceptualization (equal); Investigation (equal); Methodology (equal); Project administration (lead); Validation (equal); Visualization (equal); Writing - original draft preparation (equal); Writing – review & editing (equal). Nicolò Musso : Conceptualization (equal); Investigation (equal); Methodology (equal); Formal analysis (equal); Project administration (supporting); Validation (equal); Visualization (equal); Writing - original draft preparation (equal). Giuseppe Caruso: Investigation (equal); Methodology (equal); Formal analysis (equal); Validation (equal); Visualization (equal); Lorenzo Mattia Lazzaro : Investigation (supporting); Formal analysis (supporting); Filippo Caraci : Resources (equal);Stefania Stefani: Founding acquisition (equal);Resources (equal); Supervision (equal); Writing – review & editing (equal). Floriana Campanile : Founding acquisition (equal); Conceptualization (equal); Resources (equal); Methodology (supporting); Supervision (equal); Writing – review & editing (equal).
Acknowledgments: Some of the results of this study were presented at the 29th ECCMID (O0927) and at the 44th Italian Society of Microbiology (SIM) congress (P127). We would like to thank the BRIT laboratory at the University of Catania (Italy) for valuable technical assistance and use of their laboratories. We also wish to thank the Scientific Bureau of the University of Catania for language support. The manuscript was partially supported by: a research grant project number PRIN2017SFBFER from the Ministry of Research (MIUR) Italy; a research grant from a private company; a research grant entitled “Identification of cancer driver genes for novel diagnostics and therapeutic strategies – Piano per la ricerca 2016-2018 – Linea di intervento 2 – University of Catania, Dept. of Biomedical and Biotechnological Sciences”.
Conflicts of Interest : The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Ethics statement : None required.