Hosting for the cruel and the inconsequential

Necrotizing fasciitis: pathogenesis and treatment

Necrotizing fasciitis is a rapidly progressive, life-threatening infection and a true infectious disease emergency. Despite much clinical experience, the management of this disease remains suboptimal, with mortality rates remaining approximately 30%. Necrotizing fasciitis rarely presents with obvious signs and symptoms and delays in diagnosis enhance mortality. Therefore, successful patient care depends on the physician's acumen and index of suspicion. Prompt surgical debridement, intravenous antibiotics, fluid and electrolyte management, and analgesia are mainstays of therapy. Adjunctive clindamycin, hyperbaric oxygen therapy and intravenous immunoglobulin are frequently employed in the treatment of necrotizing fasciitis, but their efficacy has not been rigorously established. Improved understanding of the pathogenesis of necrotizing fasciitis has revealed new targets for rationally designed therapies to improve morbidity and mortality.

Interactions with fibronectin attenuate the virulence of Streptococcus pyogenes

Fibronectin-binding surface proteins are found in many bacterial species. Most strains of Streptococcus pyogenes, a major human pathogen, express the fibronectin-binding protein F1, which promotes bacterial adherence to and entry into human cells. In this study, the role of fibronectin in S. pyogenes virulence was investigated by introducing the protein F1 gene in an S. pyogenes strain lacking this gene. Furthermore, transgenic mice lacking plasma fibronectin were used to examine the relative contribution of plasma and cellular fibronectin to S. pyogenes virulence. Unexpectedly, protein F1-expressing bacteria were less virulent to normal mice, and virulence was partly restored when these bacteria were used to infect mice lacking plasma fibronectin. Dissemination to the spleen of infected mice was less efficient for fibronectin-binding bacteria. These bacteria also disseminated more efficiently in mice lacking plasma fibronectin, demonstrating that plasma fibronectin bound to the bacterial surface downregulates S. pyogenes virulence by limiting bacterial spread. From an evolutionary point of view, these results suggest that reducing virulence by binding fibronectin adds selective advantages to the bacterium.

Quantitative cytokine gene expression in human tonsils at excision and during histoculture assessed by standardized and calibrated real-time PCR and novel data processing

Real-time reverse transcription polymerase chain reaction (RT-PCR) assays were developed for the quantification of expression of the genes for human interleukin (IL)-1beta, IL-2, IL-6, IL-8, IL-10, IL-12, IL-15, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta and for the endogenous reference hydroxymethylbilane synthase (HMBS). The assays detected as little as five plasmid copies and were 100% specific. The creation and integration of a calibration sample into the assays permitted their calibration across experiments. To handle the high number of generated data, the correlator of advanced real-time assays (CARTA) software was designed to organize samples and to automatically control and analyze TaqMan real-time RT-PCR data. The RT-PCR assays were applied to quantify levels of cytokine gene expression in human palatine tonsils at excision and during 4 days of histoculture. Similar longitudinal patterns of cytokine gene expression were observed in all donors, but the variations in spontaneous expression levels between donors were large. The expression levels in histocultures were constant over time and similar to the expression levels at excision except for IL-6 and IL-8, which markedly increased following the first 24 h of culture, possibly due to the initial stress. The standardized and calibrated RT-PCR assays quantify gene expression of human cytokines proved sensitive and specific for the investigation of cell behavior at the molecular level and the newly established CARTA software, a reliable tool for rapid data handling. Tonsil histocultures could serve as a valuable ex vivo model system for further, donor-dependent, studies on activation or repression of cytokine gene expression.