Virus species polemics: 14 senior virologists oppose a proposed change to the ICTV definition of virus species

The Executive Committee of the International Committee on Taxonomy of Viruses (ICTV) has recently decided to modify the current definition of virus species (Code of Virus Classification and Nomenclature Rule 3.21) and will soon ask the full ICTV membership (189 voting members) to ratify the proposed controversial change. In this discussion paper, 14 senior virologists, including six Life members of the ICTV, compare the present and proposed new definition and recommend that the existing definition of virus species should be retained. Since the pros and cons of the proposal posted on the ICTV website are not widely consulted, the arguments are summarized here in order to reach a wider audience.     

Clinical effects of direct hemoperfusion using a polymyxin-B immobilized column in solid organ transplanted patients with signs of severe sepsis and septic shock. A pilot study

BACKGROUND: Polymyxin B (PMX-B) is a polycationic antibiotic, known to bind the lipid A portion of endotoxin, a cell wall component found exclusively in gram negative bacteria (GNB). An extracorporeal hemoperfusion device (TORAYMYXIN) has been developed: PMX is covalently bound on the surface of an insoluble carrier material so that the endotoxin can be inactivated in the blood without exerting its toxicity on the brain and kidney. The aim of this study was to clarify the efficacy, safety and clinical effects of direct hemoperfusion with an immobilized polymyxin-B fiber column (DHP-PMX) in solid organ transplanted patients with severe sepsis or septic shock. METHODS: From June 2004 to May 2005, 15 patients (10 men and 5 women), mean age 55 years old (46-65 range), underwent kidney or liver transplantation and developed severe sepsis or septic shock, as defined by the Consensus Conference of American College Physicians/Society of Critical Care Medicine (ACCP/SCCM) criteria. GNB were detected in all the patients receiving conventional treatments including antibiotic therapy, vasopressive or inotropic agents, and ventilation support. The DHP-PMX treatment was performed three times in each patient. Hemodynamic and respiratory parameters, dosage of vasopressor/inotropic drugs were assessed at baseline and after each treatment. RESULTS: No adverse events occurred. From baseline to 3rd treatment, mean arterial pressure (MAP) was increased (from 63+/-5 to 83+/-4 mmHg), while the dosage of dobutamine (from 7.5+/-3 to 3+/-2 mcg/kg/min) and noradrenaline (from 1.3+/-0.45 to 0.05+/-0.02 mcg/kg/min) were reduced. The PaO2/FiO2 ratio increased (from 234+/-38.47 to 290+/-107.48 mmHg). CONCLUSION: The use of DHP-PMX in association with conventional therapy may be an important aid in patients with sepsis.     

Solution of the time-dependent diffusion equation for a three-layer medium: application to study photon migration through a simplified adult head model

A diffusion-based model for photon migration through a three-layer medium is described. The main purpose of this work is to investigate the performance of a diffusion equation (DE)-based forward model for studying photon migration through a diffusive layered medium having a low scattering layer. This geometrical model can be used as a simple model of the adult head. Numerical results are shown for a set of values of the optical properties typical of the adult human head, where scalp and skull are lumped in the first layer while the second and third layer are associated with the cerebrospinal fluid (CSF) and the brain, respectively. Due to the presence of the CSF, which is a relatively clear layer, the diffusion-based model yields an approximate solution of photon migration. Nevertheless, comparisons with MC simulations show that the model can predict the total and the partial mean path length in the different layers with an error less than 20%. In particular, the partial mean path length in the third layer, representative of the brain, is calculated with an error less than 10% if the reduced scattering coefficient of the second layer, representative of the CSF, is assumed 0.25 mm(-1).