CcpA Affects Infectivity of \u3ci\u3eStaphylococcus aureus\u3c/i\u3e in a Hyperglycemic Environment

Many bacteria regulate the expression of virulence factors via carbon catabolite responsive elements. In Gram-positive bacteria, the predominant mediator of carbon catabolite repression is the catabolite control protein A (CcpA). Hyperglycemia is a widespread disorder that predisposes individuals to an array of symptoms and an increased risk of infections. In hyperglycemic individuals, the bacterium Staphylococcus aureus causes serious, life-threatening infections. The importance of CcpA in regulating carbon catabolite repression in S. aureus suggests it may be important for infections in hyperglycemic individuals. To test this suggestion, hyperglycemic non-obese diabetic (NOD; blood glucose level ≥20 mM) mice were challenged with the mouse pathogenic S. aureus strain Newman and the isogenic ccpA deletion mutant (MST14), and the effects on infectivity were determined. Diabetic NOD mice challenged with the ccpA deletion mutant enhanced the symptoms of infection in an acute murine pneumonia model relative to the parental strain. Interestingly, when diabetic NOD mice were used in footpad or catheter infection models, infectivity of the ccpA mutant decreased relative to the parental strain. These differences greatly diminished when normoglycemic NOD mice (blood glucose level ≤10 mM) were used. These data suggest that CcpA is important for infectivity of S. aureus in hyperglycemic individuals

Keratinocytes Determine Th1 Immunity during Early Experimental Leishmaniasis

Experimental leishmaniasis is an excellent model system for analyzing Th1/Th2 differentiation. Resistance to Leishmania (L.) major depends on the development of a L. major specific Th1 response, while Th2 differentiation results in susceptibility. There is growing evidence that the microenvironment of the early affected tissue delivers the initial triggers for Th-cell differentiation. To analyze this we studied differential gene expression in infected skin of resistant and susceptible mice 16h after parasite inoculation. Employing microarray technology, bioinformatics, laser-microdissection and in-situ-hybridization we found that the epidermis was the major source of immunomodulatory mediators. This epidermal gene induction was significantly stronger in resistant mice especially for several genes known to promote Th1 differentiation (IL-12, IL-1β, osteopontin, IL-4) and for IL-6. Expression of these cytokines was temporally restricted to the crucial time of Th1/2 differentiation. Moreover, we revealed a stronger epidermal up-regulation of IL-6 in the epidermis of resistant mice. Accordingly, early local neutralization of IL-4 in resistant mice resulted in a Th2 switch and mice with a selective IL-6 deficiency in non-hematopoietic cells showed a Th2 switch and dramatic deterioration of disease. Thus, our data indicate for the first time that epidermal cytokine expression is a decisive factor in the generation of protective Th1 immunity and contributes to the outcome of infection with this important human pathogen

CcpA Affects Infectivity of \u3ci\u3eStaphylococcus aureus\u3c/i\u3e in a Hyperglycemic Environment

Many bacteria regulate the expression of virulence factors via carbon catabolite responsive elements. In Gram-positive bacteria, the predominant mediator of carbon catabolite repression is the catabolite control protein A (CcpA). Hyperglycemia is a widespread disorder that predisposes individuals to an array of symptoms and an increased risk of infections. In hyperglycemic individuals, the bacterium Staphylococcus aureus causes serious, life-threatening infections. The importance of CcpA in regulating carbon catabolite repression in S. aureus suggests it may be important for infections in hyperglycemic individuals. To test this suggestion, hyperglycemic non-obese diabetic (NOD; blood glucose level ≥20 mM) mice were challenged with the mouse pathogenic S. aureus strain Newman and the isogenic ccpA deletion mutant (MST14), and the effects on infectivity were determined. Diabetic NOD mice challenged with the ccpA deletion mutant enhanced the symptoms of infection in an acute murine pneumonia model relative to the parental strain. Interestingly, when diabetic NOD mice were used in footpad or catheter infection models, infectivity of the ccpA mutant decreased relative to the parental strain. These differences greatly diminished when normoglycemic NOD mice (blood glucose level ≤10 mM) were used. These data suggest that CcpA is important for infectivity of S. aureus in hyperglycemic individuals

Subcutaneous infection with S. aureus in mice reveals association of resistance with influx of neutrophils and Th2 response.

Staphylococcus aureus is the leading cause of bacterial skin infection. Once it overcomes the epithelial barrier, it either remains locally controlled or spreads in the dermis causing soft tissue infection. These different courses depend not only on its virulence factors, but also on the immune response of the infected individual. The goal of this study was to identify host factors that influence different outcomes. We, therefore, established comparative analysis of subcutaneous footpad infection with S. aureus (SH1000) in different inbred mouse strains. We found that C57BL/6 mice are more susceptible than BALB/c and DBA/2 mice, reflected by significantly higher footpad swelling and bacterial load, as well as increased dissemination of bacteria into inguinal lymph nodes and kidneys. This susceptibility was associated with lower influx of polymorphonuclear leukocytes (PMNs), but higher secretion of CXCL-2. Remarkably, resistance correlated with S. aureus-specific Th2-cell response in BALB/c and DBA/2 mice, whereas susceptible C57BL/6 mice generated a Th1-cell response. As Th1 cells are able to induce release of CXCL-2, and as CXCL-2 is able to increase the survival of S. aureus within PMNs, interactions between PMNs and Th1 or Th2 cells need to be considered as important mechanisms of resistance in murine soft tissue infection with S. aureus