staphyloxanthin and Disease-Models--Animal

Selection pressures exerted on Staphylococcus aureus by host factors during infection may lead to the emergence of regulatory phenotypes better adapted to the infection site. Traits convenient for persistence may be fixed by mutation thus turning these mutants into microevolution endpoints. The feasibility that stable, non-encapsulated S. aureus mutants can regain expression of key virulence factors for survival in the bloodstream was investigated. S. aureus agr mutant HU-14 (IS256 insertion in agrC) from a patient with chronic osteomyelitis was passed through the bloodstream using a bacteriemia mouse model and derivative P3.1 was obtained. Although IS256 remained inserted in agrC, P3.1 regained production of capsular polysaccharide type 5 (CP5) and staphyloxanthin. Furthermore, P3.1 expressed higher levels of asp23/SigB when compared with parental strain HU-14. Strain P3.1 displayed decreased osteoclastogenesis capacity, thus indicating decreased adaptability to bone compared with strain HU-14 and exhibited a trend to be more virulent than parental strain HU-14. Strain P3.1 exhibited the loss of one IS256 copy, which was originally located in the HU-14 noncoding region between dnaG (DNA primase) and rpoD (sigA). This loss may be associated with the observed phenotype change but the mechanism remains unknown. In conclusion, S. aureus organisms that escape the infected bone may recover the expression of key virulence factors through a rapid microevolution pathway involving SigB regulation of key virulence factors.

Topics: Adult; Animals; Anti-Bacterial Agents; Bacteremia; Bacterial Capsules; Bacterial Proteins; Disease Models, Animal; Drug Resistance, Multiple, Bacterial; Gene Expression Regulation, Bacterial; Humans; Male; Mice; Osteomyelitis; Sequence Deletion; Staphylococcus aureus; Trans-Activators; Virulence; Virulence Factors; Xanthophylls

A central question to biology is how pathogenic bacteria initiate acute or chronic infections. Here we describe a genetic program for cell-fate decision in the opportunistic human pathogen

Topics: Animals; Bacillus subtilis; Bacterial Proteins; Base Sequence; Biofilms; Cell Differentiation; Cell Wall; Disease Models, Animal; Escherichia coli; Female; Flow Cytometry; Gene Expression Regulation, Bacterial; Genes, Bacterial; Heart; Kidney; Magnesium; Mice; Mice, Inbred BALB C; Models, Theoretical; Peptidoglycan; RNA, Bacterial; Staphylococcal Infections; Staphylococcus aureus; Teichoic Acids; Trans-Activators; Xanthophylls

Staphylococcus aureus is a major human pathogen and emergence of antibiotic resistance in clinical staphylococcal isolates raises concerns about our ability to control these infections. Cell wall-active antibiotics cause elevated synthesis of methionine sulfoxide reductases (Msrs: MsrA1 and MsrB) in S. aureus. MsrA and MsrB enzymes reduce S-epimers and R-epimers of methionine sulfoxide, respectively, that are generated under oxidative stress. In the S. aureus chromosome, there are three msrA genes (msrA1, msrA2 and msrA3) and one msrB gene. To understand the precise physiological roles of Msr proteins in S. aureus, mutations in msrA1, msrA2 and msrA3 and msrB genes were created by site-directed mutagenesis. These mutants were combined to create a triple msrA (msrA1, msrA2 and msrA3) and a quadruple msrAB (msrA1, msrA2, msrA3, msrB) mutant. These mutants were used to determine the roles of Msr proteins in staphylococcal growth, antibiotic resistance, adherence to human lung epithelial cells, pigment production, and survival in mice relative to the wild-type strains. MsrA1-deficient strains were sensitive to oxidative stress conditions, less pigmented and less adherent to human lung epithelial cells, and showed reduced survival in mouse tissues. In contrast, MsrB-deficient strains were resistant to oxidants and were highly pigmented. Lack of MsrA2 and MsrA3 caused no apparent growth defect in S. aureus. In complementation experiments with the triple and quadruple mutants, it was MsrA1 and not MsrB that was determined to be critical for adherence and phagocytic resistance of S. aureus. Overall, the data suggests that MsrA1 may be an important virulence factor and MsrB probably plays a balancing act to counter the effect of MsrA1 in S. aureus.

Topics: Animals; Anti-Bacterial Agents; Bacterial Adhesion; Cell Wall; Disease Models, Animal; Enzyme Activation; Hemolysis; Humans; Methionine Sulfoxide Reductases; Mice; Microbial Sensitivity Tests; Mutation; Oxidants; Oxidative Stress; Phagocytosis; Protein Transport; Staphylococcal Infections; Staphylococcal Protein A; Staphylococcus aureus; Xanthophylls

The defining hallmark of the newly described species, Staphylococcus argenteus, in comparison to its sister species, S. aureus and S. schweitzeri, is the absence of production of the carotenoid pigment, staphyloxanthin. Staphylococcus argenteus lacks the responsible genetic locus crtOPQMN. We examined the impact of carotenoid synthesis in two non-pigmented S. argenteus strains, MSHR1132 and SCC1165. Following complementation with a plasmid containing the carotenoid operon (pTX-crtOPQMN), compared to wild type, both complemented strains showed substantial carotenoid production, with a resultant increase in cell membrane rigidity. Surprisingly, both crtOPQMN-complemented strains exhibited increased susceptibility to the host defense peptides, LL-37 and hNP-1 in vitro, and reduced virulence in an experimental rabbit endocarditis model.

Topics: alpha-Defensins; Animals; Antimicrobial Cationic Peptides; Biosynthetic Pathways; Cathelicidins; Disease Models, Animal; Endocarditis; Genetic Complementation Test; Host-Pathogen Interactions; Operon; Plasmids; Rabbits; Staphylococcal Infections; Staphylococcus aureus; Virulence; Xanthophylls

Staphylococcus aureus clonal complex 75 (herein referred to as S. argenteus) lacks the carotenoid pigment operon, crtOPQMN, responsible for production of the putative virulence factor, staphyloxanthin. Although a common cause of community-onset skin infections among Indigenous populations in northern Australia, this clone is infrequently isolated from hospital-based patients with either bacteremic or nonbacteremic infections. We hypothesized that S. argenteus would have attenuated virulence compared to other S. aureus strains due to its staphyloxanthin "deficiency." Compared to prototypical S. aureus strains, S. argenteus was more susceptible to oxidative stress and neutrophil killing in vitro and had reduced virulence in murine sepsis and skin infection models. Transformation with pTX-crtOPQMN resulted in staphyloxanthin expression and increased resistance to oxidative stress in vitro. However, neither resistance to neutrophil killing nor in vivo virulence was increased. Thus, reduced virulence of S. argenteus in these models is due to mechanisms unrelated to lack of staphyloxanthin production.

Topics: Animals; Australia; Child; Disease Models, Animal; Genetic Complementation Test; Humans; Male; Mice; Mice, Inbred BALB C; Operon; Sepsis; Staphylococcal Infections; Staphylococcal Skin Infections; Staphylococcus aureus; Virulence; Virulence Factors; Xanthophylls