The impact of penicillinase on cefamandole treatment and prophylaxis of experimental endocarditis due to methicillin-resistant Staphylococcus aureus.

Beta-lactams active against methicillin-resistant Staphylococcus aureus (MRSA) must resist penicillinase hydrolysis and bind penicillin-binding protein 2A (PBP 2A). Cefamandole might share these properties. When tested against 2 isogenic pairs of MRSA that produced or did not produce penicillinase, MICs of cefamandole (8-32 mg/L) were not affected by penicillinase, and cefamandole had a > or =40 times greater PBP 2A affinity than did methicillin. In rats, constant serum levels of 100 mg/L cefamandole successfully treated experimental endocarditis due to penicillinase-negative isolates but failed against penicillinase-producing organisms. This suggested that penicillinase produced in infected vegetations might hydrolyze the drug. Indeed, cefamandole was slowly degraded by penicillinase in vitro. Moreover, its efficacy was restored by combination with sulbactam in vivo. Cefamandole also uniformly prevented MRSA endocarditis in prophylaxis experiments, a setting in which bacteria were not yet clustered in the vegetations. Thus, while cefamandole treatment was limited by penicillinase, the drug was still successful for prophylaxis of experimental MRSA endocarditis.

Direct angiotensin type 2 receptor (AT2R) stimulation attenuates T-cell and microglia activation and prevents demyelination in experimental autoimmune encephalomyelitis in mice.

In the present study, we evaluated stimulation of the angiotensin type 2 receptor (AT2R) by the selective non-peptide agonist Compound 21 (C21) as a novel therapeutic concept for the treatment of multiple sclerosis using the model of experimental autoimmune encephalomyelitis (EAE) in mice. C57BL-6 mice were immunized with myelin-oligodendrocyte peptide and treated for 4 weeks with C21 (0.3 mg/kg/day i.p.). Potential effects on myelination, microglia and T-cell composition were estimated by immunostaining and FACS analyses of lumbar spinal cords. The in vivo study was complemented by experiments in aggregating brain cell cultures and microglia in vitro. In the EAE model, treatment with C21 ameliorated microglia activation and decreased the number of total T-cells and CD4+ T-cells in the spinal cord. Fluorescent myelin staining of spinal cords further revealed a significant reduction in EAE-induced demyelinated areas in lumbar spinal cord tissue after AT2R stimulation. C21-treated mice had a significantly better neurological score than vehicle-treated controls. In aggregating brain cell cultures challenged with lipopolysaccharide (LPS) plus interferon-γ (IFNγ), AT2R stimulation prevented demyelination, accelerated re-myelination and reduced the number of microglia. Cytokine synthesis and nitric oxide production by microglia in vitro were significantly reduced after C21 treatment. These results suggest that AT2R stimulation protects the myelin sheaths in autoimmune central nervous system inflammation by inhibiting the T-cell response and microglia activation. Our findings identify the AT2R as a potential new pharmacological target for demyelinating diseases such as multiple sclerosis.

Use of a human-like low-grade bacteremia model of experimental endocarditis to study the role of Staphylococcus aureus adhesins and platelet aggregation in early endocarditis.

Animal models of infective endocarditis (IE) induced by high-grade bacteremia revealed the pathogenic roles of Staphylococcus aureus surface adhesins and platelet aggregation in the infection process. In humans, however, S. aureus IE possibly occurs through repeated bouts of low-grade bacteremia from a colonized site or intravenous device. Here we used a rat model of IE induced by continuous low-grade bacteremia to explore further the contributions of S. aureus virulence factors to the initiation of IE. Rats with aortic vegetations were inoculated by continuous intravenous infusion (0.0017 ml/min over 10 h) with 10(6) CFU of Lactococcus lactis pIL253 or a recombinant L. lactis strain expressing an individual S. aureus surface protein (ClfA, FnbpA, BCD, or SdrE) conferring a particular adhesive or platelet aggregation property. Vegetation infection was assessed 24 h later. Plasma was collected at 0, 2, and 6 h postinoculation to quantify the expression of tumor necrosis factor (TNF), interleukin 1α (IL-1α), IL-1β, IL-6, and IL-10. The percentage of vegetation infection relative to that with strain pIL253 (11%) increased when binding to fibrinogen was conferred on L. lactis (ClfA strain) (52%; P = 0.007) and increased further with adhesion to fibronectin (FnbpA strain) (75%; P < 0.001). Expression of fibronectin binding alone was not sufficient to induce IE (BCD strain) (10% of infection). Platelet aggregation increased the risk of vegetation infection (SdrE strain) (30%). Conferring adhesion to fibrinogen and fibronectin favored IL-1β and IL-6 production. Our results, with a model of IE induced by low-grade bacteremia, resembling human disease, extend the essential role of fibrinogen binding in the initiation of S. aureus IE. Triggering of platelet aggregation or an inflammatory response may contribute to or promote the development of IE.

Endocrine response and perceived stress test during an experimental challenge task in adult survivors of a childhood cancer.

BACKGROUND: Although long-term implications of cancer in childhood or adolescence with regard to medical conditions are well documented, the impact on mental health and on response to stress, which may be an indicator of psychological vulnerability, is not yet well understood. In this study, psychological and physiological responses to stress were examined.¦PROCEDURE: Fifty-three participants aged 18-39 years (n = 25 survivors of childhood or adolescence cancer, n = 28 controls) underwent an experimental stress test, the Trier Social Stress Test (TSST). Participants were asked to provide repeated evaluations of perceived stress on visual-analogical scales and blood samples were collected before and after the TSST to measure plasma cortisol.¦RESULTS: The psychological perception of stress was not different between the two groups. However, the cancer survivors group showed a higher global plasma cortisol level as well as higher amplitude in the response to the TSST. The global cortisol level in cancer survivors was increased when depression symptoms were present. The subjective perception of stress and the plasma cortisol levels were only marginally correlated in both groups.¦CONCLUSIONS: It is suggested that the exposure to a life-threatening experience in childhood/adolescence increases the endocrine response to stress, and that the presence of depressive symptoms is associated with an elevation of plasma cortisol levels. A better knowledge of these mechanisms is important given that the dysregulations of the stress responses may cause psychological vulnerability. Pediatr Blood Cancer 2012; 59: 138-143. © 2011 Wiley Periodicals, Inc.