Bacteremia Due to Viridans Streptococcus in Neutropenic Patients with Cancer: Clinical Spectrum and Risk Factors

Between 1988 and 1991, 26 episodes of bacteremia due to viridans streptococci occurred in 25 neutropenic patients undergoing intensive chemotherapy for hematologic malignancies. Complications related to the bacteremia were observed in 10 episodes: unilateral pulmonary infiltrates (4), acute respiratory distress syndrome (ARDS) (4), hypotension (3), and endocarditis (2). All patients with ARDS had received high doses of cytosine arabinoside and had bacteremia due to Streptococcus mitis. Death occurred in three patients (12%) but was possibly related to bacteremia in only one case. Case patients who had received prophylaxis with quinolones were compared with matched control patients who received similar prophylaxis but who did not have bacteremia due to viridans streptococci. Multivariate analysis of predisposing factors showed that high doses of cytosine arabinoside (P = .01), the presence of mucositis (P = .02), and the absence of previous therapy with parenteral antibiotics (P = .01) were independent risk factors for the development of viridans streptococcal bacteremia. Of 259 patients who had received quinolone prophylaxis during the study period, 22 (8.5%) developed an episode of viridans streptococcal bacteremia as compared with three episodes (3.7%) in 82 patients who had received a quinolone and penicillin (P = .07). However, the latter three episodes were caused by strains with decreased susceptibility to penicillin, thus suggesting that resistance to penicillin might limit the use of this antibiotic as a prophylactic agent in the futur

Bacteremia due to viridans streptococcus in neutropenic patients with cancer: clinical spectrum and risk factors.

Between 1988 and 1991, 26 episodes of bacteremia due to viridans streptococci occurred in 25 neutropenic patients undergoing intensive chemotherapy for hematologic malignancies. Complications related to the bacteremia were observed in 10 episodes: unilateral pulmonary infiltrates (4), acute respiratory distress syndrome (ARDS) (4), hypotension (3), and endocarditis (2). All patients with ARDS had received high doses of cytosine arabinoside and had bacteremia due to Streptococcus mitis. Death occurred in three patients (12%) but was possibly related to bacteremia in only one case. Case patients who had received prophylaxis with quinolones were compared with matched control patients who received similar prophylaxis but who did not have bacteremia due to viridans streptococci. Multivariate analysis of predisposing factors showed that high doses of cytosine arabinoside (P = .01), the presence of mucositis (P = .02), and the absence of previous therapy with parenteral antibiotics (P = .01) were independent risk factors for the development of viridans streptococcal bacteremia. Of 259 patients who had received quinolone prophylaxis during the study period, 22 (8.5%) developed an episode of viridans streptococcal bacteremia as compared with three episodes (3.7%) in 82 patients who had received a quinolone and penicillin (P = .07). However, the latter three episodes were caused by strains with decreased susceptibility to penicillin, thus suggesting that resistance to penicillin might limit the use of this antibiotic as a prophylactic agent in the future

Rhombohedral structure of highly ordered and oriented self-assembled nanoporous silica thin films

Nanoporous silica films have been synthesized by self-assembly on substrates by dip-coating from a combined solution of aged silica oligomers and poly(ethylene oxide)(20)-poly(propylene oxide)(70)-poly(ethylene oxides)(20) triblock copolymer (Pluronic P123) in ethanol and water. The films are indexed with the rhombohedral space group R3m and are oriented through the thickness of the film with the (111) axis perpendicular to the substrate. Sixfold symmetry perpendicular to the substrate is directly observed by high-resolution top-view field emission scanning electron microscopy over the entire substrate. The films have domains that sample many orientations in the plane of the substrate resulting in a reciprocal space composed of rings. These rings are directly observed by collecting small-angle X-ray scattering data at many angles of incidence from transmission (beam perpendicular to the substrate) all the way down to the grazing angle of incidence. At each rotation, the Bragg spot location in the two-dimensional pattern is quantitatively predicted by an Rim unit cell with lattice constants a = 112 angstrom and alpha = 86 degrees. On the basis of these lattice constants, it is conjectured that the rhombohedral structure results from a uniaxial contraction of a (111) oriented film of self-assembled aggregates ordered on a face-centered cubic lattice. The film structure and orientation reported here differ from previous reports of cubic, or distorted cubic, nanoporous films synthesized with P123 and F127 and are expected to be important steps in controlling structure and accessibility in nanoporous films

Simulation and interpretation of 2D diffraction patterns from self-assembled nanostructured films at arbitrary angles of incidence: From grazing incidence (above the critical angle) to transmission perpendicular to the substrate

A method to calculate the location of all Bragg diffraction peaks from nanostructured thin films for arbitrary angles of incidence from just above the critical angle to transmission perpendicular to the film is reported. At grazing angles, the positions are calculated using the distorted wave Born approximation (DWBA), whereas for larger angles where the diffracted beams are transmitted though the substrate, the Born approximation ( BA) is used. This method has been incorporated into simulation code ( called NANOCELL) and may be used to overlay simulated spot patterns directly onto two-dimensional (2D) grazing angle of incidence small-angle X-ray scattering (GISAXS) patterns and 2D SAXS patterns. The GISAXS simulations are limited to the case where the angle of incidence is greater than the critical angle (alpha(i) \u3e alpha(c)) and the diffraction occurs above the critical angle (alpha(f) \u3e alpha(c)). For cases of surfactant self-assembled films, the limitations are not restrictive because, typically, the critical angle is around 0.2 degrees but the largest d spacings occur around 0.8 degrees 2 theta. For these materials, one finds that the DWBA predicts that the spot positions from the transmitted main beam deviate only slightly from the BA and only for diffraction peaks close the critical angle. Additional diffraction peaks from the reflected main beam are observed in GISAXS geometry but are much less intense. Using these simulations, 2D spot patterns may be used to identify space group, identify the orientation, and quantitatively fit the lattice constants for SAXS data from any angle of incidence. Characteristic patterns for 2D GISAXS and 2D low-angle transmission SAXS patterns are generated for the most common thin film structures, and as a result, GISAXS and SAXS patterns that were previously difficult to interpret are now relatively straightforward. The simulation code (NANOCELL) is written in Mathematica and is available from the author upon request