Contribution of Tumor Necrosis Factor to Host Defense against Staphylococci in a Guinea Pig Model of Foreign Body Infections

The contribution of the cytokine tumor necrosis factor (cachectin; TNF) to host defenses against staphylococcal foreign body infections was studied in vivo. In tissue cages subcutaneously implanted into guinea pigs, progressive infection was initiated by a very low inoculum (100 cfu) of Staphylococcus aureus with a success rate of 100%, as is frequently encountered in related clinical situations. Locally injected autologous bacterial components derived from the cell wall of S. aureus, in particular peptidoglycan, were very active in raising TNF levels in tissue cage fluid and in preventing the development of infection by the 100% infective dose of the test strain. Furthermore, injection of murine recombinant TNF into tissue cages could substitute for the bacterial components in preventing experimental infection by S. aureus. The protective effect of TNF-eliciting bacterial components could be neutralized by anti-TNF antibodies. A local increase in TNF levels might improve host defenses against staphylococcal foreign body infection

Host Factors Selectively Increase Staphylococcal Adherence on Inserted Catheters: A Role for Fibronectin and Fibrinogen or Fibrin

Intravascular catheters are prone to staphylococcal infections. To study the role in staphylococcal adherence played by fibrinogen or fibrin and fibronectin deposited on inserted catheters, 187 peripheral or central cannulae were prospectively removed from hospitalized patients. Compared with uninserted catheters, which allowed only minimal adherence, previously inserted catheters promoted significant adherence of staphylococcal isolates from patients with intravenous device infections. Adhesion-promoting properties were studied with laboratory strains having well-defined affinities for either fibronectin or fibrinogen adherence of Staphylococcus aureus Cowan I, which has the highest affinity for both adhesins, was more strongly promoted (10- to 50-fold) on inserted cannulae than was that of S. aureus Wood 46 (4- to lO-fold) or Staphylococcus epidermidis Rp 12 (2.2-fold), which has no affinity for fibrinogen but does for fibronectin. Although all types of cannulae contained significant amounts of fibrin, which may promote adherence of coagulase-positive staphylococci, results obtained with coagulase-negative isolates suggested that in vivo-deposited fibronectin is also a critical determinant in this proces

Bad news from Fallujah

This study uses the thematic analysis developed by the Glasgow University Media Group to explore how the US, UK and German national press covered the US/Coalition assault on the Iraqi city of Fallujah in November 2004. The study relies on quantitative and qualitative full text content analyses to assess 428 news, editorial and commentary items. The article suggests that, while government and military officials of the US/Coalition had argued the military ‘operation’ was necessary to secure Iraq and defeat an ‘insurgency’, organisations and actors from Iraqi society refer to the ‘operation’ as ‘collective punishment’ and a ‘massacre’ that targeted the Iraqi population. The article investigates how the press represented each of these perspectives. The findings suggest that the press overemphasised the US/Coalition perspective despite striking counter evidence. Critical aspects of coverage largely focused on tactical elements of the military dimension of the event. The article concludes that such findings are in accord with hegemonic models of media performance

Attachment of Staphylococcus aureus to polymethylmethacrylate increases its resistance to phagocytosis in foreign body infection.

The mechanisms responsible for the development of a pyogenic infection (most commonly due to staphylococci) in the vicinity of an implanted foreign body have been studied recently by several investigators. Thus, we have been able to demonstrate that the phagocytic function of residential polymorphonuclear leukocytes (PMN) is deficient in the presence of a foreign body. Others have shown that in the presence of foreign surfaces, microorganisms produce extracellular amorphous material, the pathogenic role of which is still to be defined. In the present study we use a novel assay system to demonstrate that Staphylococcus aureus Wood 46, after attachment to polymethylmethacrylate (PMMA), shows increased resistance to the phagocytic-bactericidal action of normal PMN. The first step of this assay involves the reproducible attachment of [3H]thymidine-labeled bacteria to PMMA cover slips. During the second step, attached bacteria were exposed to guinea pig peritoneal exudate PMN. In the third and final step, attached S. aureus cells were removed from the cover slips using a procedure harmless to the bacteria. The extent of bacterial detachment was estimated by radioactive counts and their viability by standard colony counts. Whereas bacteria that were attached artificially and rapidly by centrifugation and immediately exposed to PMN were killed in the phagocytic assay, bacteria adhering spontaneously to the cover slips for a prolonged period of time were more resistant to the killing action of the phagocytes. The spontaneous adherence of S. aureus to PMMA renders it poorly susceptible to the killing action of PMN