ImportanceSurgical site infection (SSI) complicates 2-5% of surgeries in the United States. Severity of SSI ranges from superficial skin infection to life-threatening conditions such as severe sepsis, and SSIs are responsible for increased morbidity, mortality, and economic burden associated with surgery. Staphylococcus aureus (S. aureus) is a commonly-isolated organism for SSI, and methicillin-resistant S. aureus SSI incidence is increasing globally.ObjectiveThe objective of this systematic review was to characterize risk factors for SSI within observational studies describing incidence of SSI in a real-world setting.Evidence ReviewAn initial search identified 328 titles published in 2002-2012; 57 were identified as relevant for data extraction. Extracted information included study design and methodology, reported cumulative incidence and post-surgical time until onset of SSI, and odds ratios and associated variability for all factors considered in univariate and/or multivariable analyses. FindingsMedian SSI incidence was 3.7%, ranging from 0.1% to 50.4%. Incidence of overall SSI and S. aureus SSI were both highest in tumor-related and transplant surgeries. Median time until SSI onset was 17.0 days, with longer time-to-onset for orthopedic and transplant surgeries. Risk factors consistently identified as associated with SSI included co-morbidities, advanced age, risk indices, patient frailty, and surgery complexity. Thirteen studies considered diabetes as a risk factor in multivariable analysis; 85% found a significant association with SSI, with odds ratios ranging from 1.5-24.3. Longer surgeries were associated with increased SSI risk, with a median odds ratio of 2.3 across 11 studies reporting significant results.Conclusions and RelevanceIn a broad review of published literature, risk factors for SSI were characterized as describing reduced fitness, patient frailty, surgery duration, and complexity. Recognition of risk factors frequently associated with SSI allows for identification of such patients with the greatest need for optimal preventive measures to be identified and pre-treatment prior to surgery.
Fusion of myeloma cells and B lymphocytes to form hybridomas which produce monoclonal antibodies has been a major advance, but the poor efficiency and randomness of viral or polyethylene glycol fusion techniques generally gives poor yields of specific, high affinity antibodies. High voltage electrical fields with dielectrophoresis to ensure cell alignment can fuse a limited number of cells under direct microscopic examination, but it is not possible to identify B-cells destined to secrete relevant antibodies. However, B-cells express, on their surface, antigen receptor immunoglobulins of the same antigenic specificity as the secreted antibodies. Binding of antigen to surface immunoglobulins stimulates proliferation and differentiation of B-cells into plasma cells. Here we report the use of the selective, high affinity interaction of antigen with surface immunoglobulins on B-cells to facilitate a close adherence to myeloma cells. The antigen, covalently conjugated to avidin, binds to the surface immunoglobulins on B-cells. This B-cell-antigen-avidin complex binds to biotin covalently attached to the surface of myeloma cells. An intense electric field across a bulk cell suspension then produces selective fusion of cells in contact, that is, of myeloma cells with B-cells which make the appropriate antibody. We have used this technique with several antigens, and all resultant hybridomas secrete appropriate antibodies with very high affinity.
Expression of tau protein in non-neuronal cells can result in a redistribution of the microtubule cytoskeleton into thick bundles of tau-containing microtubules (Lewis et al.: Nature 342:498-505, 1989; Kanai et al.: J Cell Biol 109:1173-1184, 1989). We reconstituted microtubule bundles using purified tubulin and tau in order to study the assembly of these structures. Taxol-stabilized tubulin polymers were incubated with various concentrations of recombinant human tau and examined by electron microscopy. With increasing concentrations of tau 3 (tau isoform containing three microtubule binding domains) or tau 4 (isoform containing four microtubule binding domains) the microtubules changed orientation from a random distribution to loosely and tightly packed parallel arrays and then to thick cables. In contrast, tau 4L, the tau isoform containing four microtubule binding domains plus a 58-amino acid insert near the N-terminus, showed minimal bundling activity. tau 4-induced bundling could be inhibited by the addition of 0.5 M NaCl or 0.4 mM estramustine phosphate, conditions which are known to inhibit tau binding to microtubules. A tau construct that contained only the microtubule binding domains plus 19 amino acids to the C-terminus was fully capable of bundling microtubules. Phosphorylation of tau 3 with cAMP-dependent protein kinase had no effect on its ability to induce microtubule bundling. These results indicate that tau protein is directly capable of bundling microtubules in vitro, and suggests that different tau isoforms differ in their ability to bundle microtubule filaments.
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