Comparison of Staphylococcus aureus strains for ability to cause infective endocarditis and lethal sepsis in rabbits.

Staphylococcus aureus is a major cause of infective endocarditis (IE) and sepsis. Both methicillin-resistant (MRSA) and methicillin-sensitive (MSSA) strains cause these illnesses. Common S.

Generation of virulence factor variants in Staphylococcus aureus biofilms.

Several serious diseases are caused by biofilm-associated Staphylococcus aureus. Colonial variants occur in biofilms of other bacterial species, and S. aureus variants are frequently isolated from biofilm-associated infections.

Delays in Pseudomonas aeruginosa quorum-controlled gene expression are conditional.

Acyl-homoserine lactone (acyl-HSL) signaling is thought to mediate quorum sensing in many species of Proteobacteria. The opportunistic human pathogen Pseudomonas aeruginosa uses acyl-HSLs to regulate hundreds of genes, including many that code for extracellular virulence factors. The idea that the P.

Characterization of virulence factor regulation by SrrAB, a two-component system in Staphylococcus aureus.

Workers in our laboratory have previously identified the staphylococcal respiratory response AB (SrrAB), a Staphylococcus aureus two-component system that acts in the global regulation of virulence factors. This system down-regulates production of agr RNAIII, protein A, and toxic shock syndrome toxin 1 (TSST-1), particularly under low-oxygen conditions. In this study we investigated the localization and membrane orientation of SrrA and SrrB, transcription of the srrAB operon, the DNA-binding properties of SrrA, and the effect of SrrAB expression on S.

Quorum sensing in Staphylococcus aureus biofilms.

Several serious diseases are caused by biofilm-associated Staphylococcus aureus, infections in which the accessory gene regulator (agr) quorum-sensing system is thought to play an important role. We studied the contribution of agr to biofilm development, and we examined agr-dependent transcription in biofilms. Under some conditions, disruption of agr expression had no discernible influence on biofilm formation, while under others it either inhibited or enhanced biofilm formation.

Quorum sensing in Staphylococcus infections.

Quorum sensing via the accessory gene regulator (agr) system has been assigned a central role in the pathogenesis of staphylococci, particularly Staphylococcus aureus. While the control of virulence gene expression in vitro by agr has been relatively straightforward to describe, regulation of both the quorum response itself and virulence genes in vivo is considerably more complex. The quorum response is highly dependent upon the environment in which the organism is grown and is strongly influenced by additional regulators that respond to signals other than cell density.

Characterization and expression analysis of Staphylococcus aureus pathogenicity island 3. Implications for the evolution of staphylococcal pathogenicity islands.

We describe the complete sequence of the 15.9-kb staphylococcal pathogenicity island 3 encoding staphylococcal enterotoxin serotypes B, K, and Q. The island, which meets the generally accepted definition of pathogenicity islands, contains 24 open reading frames potentially encoding proteins of more than 50 amino acids, including an apparently functional integrase.

Repression of the Staphylococcus aureus accessory gene regulator in serum and in vivo.

Subgenomic DNA microarrays were employed to evaluate the expression of the accessory gene regulator (agr locus) as well as multiple virulence-associated genes in Staphylococcus aureus. Gene expression was examined during growth of S. aureus in vitro in standard laboratory medium and rabbit serum and in vivo in subcutaneous chambers implanted in either nonimmune rabbits or rabbits immunized with staphylococcal enterotoxin B.