Staphylococcus aureus colonizes epithelial surfaces, but it can also cause severe
infections. The aim of this work was to investigate whether bacterial virulence correlates with defined types of tissue
infections. For this, we collected 10⁻12 clinical S. aureus strains each from nasal colonization, and from patients with
endoprosthesis infection, hematogenous
osteomyelitis, and
sepsis. All strains were characterized by genotypic analysis, and by the expression of
virulence factors. The host⁻pathogen interaction was studied through several functional assays in osteoblast cultures. Additionally, selected strains were tested in a murine
sepsis/
osteomyelitis model. We did not find characteristic bacterial features for the defined
infection types; rather, a wide range in all strain collections regarding cytotoxicity and invasiveness was observed. Interestingly, all strains were able to persist and to form small colony variants (SCVs). However, the low-cytotoxicity strains survived in higher numbers, and were less efficiently cleared by the host than the highly cytotoxic strains. In summary, our results indicate that not only destructive, but also low-cytotoxicity strains are able to induce
infections. The low-cytotoxicity strains can successfully survive, and are less efficiently cleared from the host than the highly cytotoxic strains, which represent a source for
chronic infections. The understanding of this interplay/evolution between the host and the pathogen during
infection, with specific attention towards low-cytotoxicity isolates, will help to optimize treatment strategies for invasive and
therapy-refractory
infection courses.