Augmented expression of polysaccharide intercellular adhesin in a defined Staphylococcus epidermidis mutant with the small-colony-variant phenotype.
While coagulase-negative staphylococci (CoNS), with their ability to form a thick, multilayered biofilm on foreign bodies, have been identified as the major cause of implant-associated infections, no data are available about biofilm formation by staphylococcal small-colony variants (SCVs). In the past years, a number of device-associated infections due to staphylococcal SCVs were described, among them, several pacemaker infections due to SCVs of CoNS auxotrophic to hemin. To test the characteristics of SCVs of CoNS, in particular, to study the ability of SCVs to form a biofilm on foreign bodies, we generated a stable mutant in electron transport by interrupting one of the hemin biosynthetic genes, hemB, in Staphylococcus epidermidis. In fact, this mutant displayed a stable SCV phenotype with tiny colonies showing strong adhesion to the agar surface. When the incubation time was extended to 48 h or a higher inoculum concentration was used, the mutant produced biofilm amounts on polystyrene similar to those produced by the parent strain. When grown under planktonic conditions, the mutant formed markedly larger cell clusters than the parental strain which were completely disintegrated by the specific beta-1,6-hexosaminidase dispersin B but were resistant to trypsin treatment. In a dot blot assay, the mutant expressed larger amounts of polysaccharide intercellular adhesin (PIA) than the parent strain. In conclusion, interrupting a hemin biosynthetic gene in S. epidermidis resulted in an SCV phenotype. Markedly larger cell clusters and the ability of the hemB mutant to form a biofilm are related to the augmented expression of PIA.
Al Laham
Nahed
N
Institute of Medical Microbiology, University Hospital of Münster, Domagkstr. 10, 48149 Münster, Germany.
Rohde
Holger
H
Sander
Gunnar
G
Fischer
Andreas
A
Hussain
Muzaffar
M
Heilmann
Christine
C
Mack
Dietrich
D
Proctor
Richard
R
Peters
Georg
G
Becker
Karsten
K
von Eiff
Christof
C
D001422:Bacterial Adhesion / Q000502:physiology; D001426:Bacterial Proteins / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development*; D017353:Gene Deletion; D006026:Glycoside Hydrolases / Q000378:metabolism; D006427:Hemin / Q000235:genetics; D015151:Immunoblotting; D009024:Morphogenesis / Q000235:genetics*; D016254:Mutagenesis, Insertional; D009154:Mutation; D010641:Phenotype; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis* / Q000235:genetics / Q000502:physiology; D013212:Staphylococcus epidermidis / Q000235:genetics / Q000254:growth & development* / Q000502:physiology*; D014357:Trypsin / Q000378:metabolism
D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; C113579:polysaccharide intercellular adhesin; D006427:Hemin; D006026:Glycoside Hydrolases; C501330:dispersin B, Actinobacillus actinomycetemcomitans; D014357:Trypsin