The role of sigmaB in persistence of Staphylococcus epidermidis foreign body infection.
Staphylococcal biofilm formation depends on the transcription factor sigma(B). We further investigated the role of sigma(B) in biofilm formation and persistence in vitro and in vivo in a subcutaneous rat model. As expected, expression of all sigma(B) operon genes was transiently higher in the first 6 h of biofilm formation compared to planktonic bacteria, concurrent with a temporary upregulation of icaA and aap expression. However, we also observed a second upregulation of sigB expression in biofilm more than 2 days old without upregulation of icaA or aap. Biofilm formation by Staphylococcus epidermidis strains 8400 and 1457 was compared to that of isogenic mutants with inactivation of rsbU, of rsbUVW and of the entire sigma(B) operon. Both wild-type strains and the constitutively sigB-expressing rsbUVW mutant showed a strong biofilm-positive phenotype. The rsbUVW mutant biofilm was, however, thinner and more evenly spread than the wild-type biofilm. Inactivation of SigB in the rsbUVWsigB mutant or mutation of the positive regulator RsbU reduced both the number of sessile bacteria and polysaccharide intercellular adhesin (PIA) synthesis. These differences between the wild-types and their respective mutants appeared after 6 h in in vitro biofilms but only after 4 days in in vivo biofilms. Our results provide additional evidence for a role for sigma(B) in biofilm formation. They also suggest a role for sigma(B) in biofilm maturation and stability that is independent of PIA or accumulation-associated protein (Aap) and point to significant differences in the temporal development between in vitro and in vivo biofilms.
Pintens
Valerie
V
Department of Medical Diagnostics, Laboratory of Clinical and Experimental Microbiology, KULeuven, UZ Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
Massonet
Caroline
C
Department of Medical Diagnostics, Laboratory of Clinical and Experimental Microbiology, KULeuven, UZ Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
Merckx
Rita
R
Department of Medical Diagnostics, Laboratory of Clinical and Experimental Microbiology, KULeuven, UZ Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
Vandecasteele
Stefaan
S
Department of Internal Medicine and Infectious Diseases, AZ Sint-Jan AV, Ruddershove 10, B-8000 Brugge, Belgium.
Peetermans
Willy E
WE
Department of Internal Medicine, UZ Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.
Knobloch
Johannes K-M
JK
Institut für Medizinische Mikrobiologie und Hygiene, Universität Lübeck, 23538 Lübeck, Germany.
Van Eldere
Johan
J
Department of Medical Diagnostics, Laboratory of Clinical and Experimental Microbiology, KULeuven, UZ Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium.