Transposon Mutants of Staphylococcus epidermidis Deficient in Elaboration of Capsular Polysaccharide/Adhesin and Slime Are Avirulent in a Rabbit Model of Endocarditis

Abstract

Virulence comparisons were made in a rabbit model of endocarditis between wild-type and transposon mutants of Staphylococcus epidermidis deficient in elaboration of the capsular polysaccharide/adhesin (PS/A) and slime. The parental phenotype grew from 36 (61%) of 59 cultures of blood. The PS/A-negative phenotype grew in 1 (1%) of 98 cultures of blood (P < .001). No animals infected with PS/A-negative strains developed endocarditis compared with 75% of rabbits infected with PS/A-positive strains. PS/A-producing strains survived better than did PS/A-deficient strains in intact, absorbed rabbit or human serum plus human leukocytes. There was also greater deposition of C3 onto the PS/A-deficient strains than with the PS/A-producing isogenic strains. PS/A functions as an antiphagocytic bacterial capsule preventing C3 deposition and phagocytosis; loss of this structure increases the strain's susceptibility to opsonic killing and decreases its virulence.

Identification of Streptococcus sanguinis Genes Required for Biofilm Formation and Examination of Their Role in Endocarditis Virulence

“…Moreover, biofilm formation in vitro can be correlated with virulence in vivo (43,66). Native-valve endocarditis caused by viridans group streptococci may not fit the strict definition of a biofilm.…”

Host-Bacteria Interactions in Foreign Body Infections

“…17 Most in vitro studies of CNS attachment and colonization of artificial surfaces were carried out in the absence of any protein coating and have focused on either slime production or describing a capsular surface polysaccharide that promotes adhesion to uncoated plastic. 41,42 During the past 15 years, our group studied the role of plasma or extracellular matrix proteins, in particular, fibronectin, fibrinogen, or fibrin, in promoting S aureus (and to some extent S epidermidis) adhesion to implanted or inserted foreign materials. 25 For in vivo studies, our group used PMMA coverslips that were inserted in subcutaneously implanted tissue cages as described above.…”

Staphylococcus aureus Develops an Alternative, ica- Independent Biofilm in the Absence of the arlRS Two-Component System

“…Inside the biofilm, S. aureus becomes more resistant to antibiotic treatments and the actions of the immune system (2, 23). As a consequence, staphylococcal-biofilm-associated infections of this type are difficult to eradicate, and most of them can be eliminated only by the removal and substitution of the contaminated implant.With the exception of the icaADBC operon, discovered by heterologous complementation of a biofilm-negative Staphylococcus carnosus isolate with a genomic library of Staphylococcus epidermidis RP62A (29), early genetic studies of the staphylococcal-biofilm formation process have been performed using transposon mutagenesis on a biofilm-positive isolate and the ensuing selection of biofilm-deficient mutants by a microtiter plate assay (6,13,24,27,28,37,38,42,46,49). These studies have been crucial for identifying S. aureus genes whose presence is essential for primary attachment and/or biofilm development under the environmental conditions used during the screening process.…”