Staphylococcus aureus small-colony variants are adapted phenotypes for intracellular persistence.
BACKGROUND
Staphylococcus aureus is an important human pathogen of endovascular diseases, which can take a chronic course with a high relapse rate despite antimicrobial treatment. Thus far, persistent and antibiotic-refractory infections have been largely associated with a subpopulation of S. aureus, the small-colony variants (SCVs).


METHODS
In this work, we used endothelial cells to investigate infection with the highly virulent wild-type isolate (6850), 2 stable isogenic SCV phenotypes (hemB mutant IIb13 and JB1), and the complemented mutant.


RESULTS
All strains were highly invasive in endothelial cells but largely differed in host response induction. Microarray analysis showed that wild-type phenotypes up-regulated a large number of endothelial genes (including genes involved in innate immunity), whereas the SCVs did not cause these dramatic changes. The inflammatory response and cytotoxicity were strongest shortly after infection and largely decreased within the following days, which was accompanied by a fast elimination of intracellular wild-type bacteria. By contrast, SCVs survived within endothelial cells at high numbers.


CONCLUSIONS
S. aureus intracellular persistence via the development of an adapted subpopulation of SCVs most likely represents an important strategy of S. aureus to hide within the host cells, which could be a reservoir for chronic infections.
Tuchscherr
Lorena
L
Institutes of Medical Microbiology, Center of Clinical Research, University Hospital of Münster, Münster, Germany.
Heitmann
Vanessa
V
Hussain
Muzaffar
M
Viemann
Dorothee
D
Roth
Johannes
J
von Eiff
Christof
C
Peters
Georg
G
Becker
Karsten
K
Löffler
Bettina
B
D002478:Cells, Cultured; D003593:Cytoplasm / Q000382:microbiology*; D042783:Endothelial Cells / Q000382:microbiology*; D020869:Gene Expression Profiling; D054884:Host-Pathogen Interactions; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D013211:Staphylococcus aureus / Q000254:growth & development* / Q000472:pathogenicity*