Failure of bacterial screening to detect Staphylococcus aureus: the English experience of donor follow-up.

BACKGROUND AND OBJECTIVES: Between February 2011 and December 2016, over 1·6 million platelet units, 36% pooled platelets, underwent bacterial screening prior to issue. Contamination rates for apheresis and pooled platelets were 0·02% and 0·07%, respectively. Staphylococcus aureus accounted for 21 contaminations, including four pooled platelets, one confirmed transfusion-transmitted infection (TTI) and three 'near-miss' incidents detected on visual inspection which were negative on screening. We describe follow-up investigations of 16 donors for skin carriage of S. aureus and molecular characterisation of donor and pack isolates. MATERIALS AND METHODS: Units were screened by the BacT/ALERT 3D detection system. Contributing donors were interviewed and consent requested for skin and nasal swabbing. S. aureus isolates were referred for spa gene type and DNA macrorestriction profile to determine identity between carriage strains and packs. RESULTS: Donors of 10 apheresis and two pooled packs screen positive for S. aureus were confirmed as the source of contamination; seven had a history of skin conditions, predominantly eczema; 11 were nasal carriers. The 'near-miss' incidents were associated with apheresis donors, two donors harboured strains indistinguishable from the pack strain. The TTI was due to a screen-negative pooled unit, and a nasal isolate of one donor was indistinguishable from that in the unit. CONCLUSION: Staphylococcus aureus contamination is rare but potentially harmful in platelet units. Donor isolates showed almost universal correspondence in molecular type with pack isolates, thus confirming the source of contamination. The importance of visual inspection of packs prior to transfusion is underlined by the 'near-miss' incidents.

Detection of malarial DNA in blood donors--evidence of persistent infection.

BACKGROUND AND OBJECTIVES: The English transfusion service has screened donations from malaria-risk donors for malarial antibodies for over 10 years. The donor population includes migrants from many malaria-endemic countries and, from our experiences with post-transfusion malaria, some of these may remain parasitaemic and need clinical review. MATERIALS AND METHODS: Malarial antibody screen-reactive donations with serological evidence of malaria identified by the reference laboratory were further investigated for the presence of malarial DNA. RESULTS: Malarial DNA was found in 14 of 1955 samples investigated; three P. falciparum, five P. vivax, three P. ovale, two P. malariae and one dual parasitaemia P. falciparum/P. malariae. All of these were donors whose malaria risk was residency rather than travel. CONCLUSION: Malarial parasitaemia in healthy donors occurs, and donor malaria-risk strategies must take into account the possibility of such donors presenting. Countries not utilizing malarial antibody screening should consider carefully the collection of donations from donors previously resident in endemic countries; temporary deferral is insufficient.

Catching CO2 in a bowl.

Increased concentrations of CO(2) in the atmosphere contribute to global climate change. Improved methods are needed for removing CO(2) from the flue gas of power plants and/or directly from the atmosphere. A macrocyclic amidourea recently synthesized by Brooks et al., when dissolved in DMSO along with tetrabutyl ammonium fluoride, removes CO(2) from the atmosphere to form a complex in which a CO(3) group is held by a number of O-H-N bonds within the bowl-shaped cavity of the macrocycle. We have calculated the structure, stability, and vibrational spectra of this complex, using density functional techniques and polarized double-zeta basis sets. Both basis set superposition errors and polarizable continuum effects on the complex geometry and stability have been evaluated. The calculated structure is in good agreement with experiment. We predict that this CO(3)(-2) complex (and its HCO(3)(-) analogue) have larger formation constants by several orders of magnitude than the analogue complex of the amidourea macrocycle with Cl(-) (particularly in DMSO solution compared to aqueous solution). Our calculations also indicate that the CO(3)(-2) and HCO(3)(-) complexes can be distinguished by (13)C NMR. The CO(3)(-2) complex also has a distinctive H-N stretch, perturbed by the H-bonding to the CO(3) group. We also calculate the CO(3)(-2) complex to absorb within the visible region, unlike the free macrocycle or typical metal carbonates. Macrocycles of this type may provide a useful route to the absorption of atmospheric CO(2). Our calculations also indicate that changing the solvent from DMSO to water and/or heating the complex will be an efficient way to decompose it to release CO(2).

H2CO3(s): a new candidate for CO2 capture and sequestration.

To reduce the magnitude of anthropogenic global warming it is necessary to remove CO2(g) from the effluent streams of coal-fired power plants and to sequester the CO2 either as a liquid or by reaction with other compounds. A major difficulty in achieving this goal arises from the very weak acidity of CO2(g), causing it to react only incompletely with weak bases, although this weak interaction does provide a means for "stripping" the CO2 from the acid-base complex at high temperatures. Reaction with strong bases like Na0H yields more stable complexes, but massive amounts of chemical reactants would need to be purchased and chemical products like NaHCO3 then stored. However, when gas-phase CO2 reacts with the weak base water (or when bicarbonate reacts with strong acid) the unstable product monomeric "H2CO3" can be formed. The free energy required is about 16 kcal/mol in the gas phase and about 10 kcal/mol in aqueous solution. This energy can be supplied by particle or photon excitation and is only a small fraction ofthe energy released when a mole of CH4 is converted to a mole of CO2. Although this monomeric compound is highly unstable, its oligomers are considerably more stable, due to internal H-bonding, with free energies for the larger oligomers in the gas phase which are about 4 kcal/(mol of H2CO3) lower, only about 6 kcal/mol H2CO3 higher than the gas-phase combination of CO2 and H2O at room temperature. Also, at lower temperature the entropic penalty for the oligomer is less and oligomeric H2CO3 becomes stable around the sublimation temperature of dry ice. This indicates that it may be possible to capture gas-phase CO2 directly, using only cheap and abundant H2O as a reactant, and to store the resulting (H2CO3)n as a oligomeric solid at only moderately cold temperatures. These conclusions are based on quantum computations that accurately reproduce the structures, spectra, and stabilities of H2CO3 oligomers. Methods for producing and characterizing the H2CO3 oligomers are discussed. However, some aspects of the proposed scheme are quite speculative and will require additional investigation. Several important questions need to be answered before the feasibility of this procedure on a planetary scale can be assessed, particularly those involving the vapor pressure curve, heat of sublimation, density, and compressibility of (H2CO3)n.

H2CO3 and its oligomers: structures, stabilities, vibrational and NMR spectra, and acidities.

Although the molecular form of carbonic acid, H2CO3, is of very limited stability in aqueous solution, some form of H2CO3 is apparently stable as a solid and may be a stable species on acid-treated carbonate mineral surfaces. Experimental vibrational spectra that have been assigned to solid H2CO3 have been obtained by several research groups, although there is no information on either the local or long-range structure of this phase and calculated vibrational frequencies for monomeric H2CO3 show significant discrepancies with the experimental IR data. Previous calculations have also indicated that H-bonded H2CO3oligomers are more stable than the monomer and have significantly different vibrational spectra, but the accuracy of the spectral calculations was not considered sufficient to reassign the experimental data. We have now calculated the harmonic vibrational spectrum of monomeric H2CO3 at the 6-311+G(2d,p) CCSD level and have calculated anharmonic corrections at the CBSB7 B3LYP level (used in CBS-QB3 calculations), combining the two to obtain an accurate description of the fundamental vibrations of gas phase H2CO3, which disagree significantly and systematically with the experimental data for solid H2CO3. For the H-bonded dimer, H2CO3(2), we have calculated both the harmonic spectrum and anharmonicity corrections at the CBSB7 B3LYP level, finding much better agreement with the experimental spectrum of solid H2CO3 than for the monomer, particularly for the C=O and O-H stretching vibrations, which are strongly red-shifted by both H bonding and anharmonic effects in the dimer. The free-energy changes for the formation of the H2CO3(n) (n = 2 and 3) oligomers and for the formation of a 1D chain structure of H-bonded monomers are negative in the gas phase, despite an unfavorable entropic contribution. However, in aqueous solution, the free-energy change for the formation of the n = 2 and 3 oligomers becomes positive because of the loss of hydration free energy, since the -OH groups of H2CO3 are removed from H bonding with the solvent. We have also calculated 13C NMR shieldings for the H2CO3 oligomers and some other related molecules, finding that the central C is systematically deshielded by oligomerization.

Calculation of the energetics for the oligomerization of gas phase HgO and HgS and for the solvolysis of crystalline HgO and HgS.

Recent experimental studies indicate that gaseous elemental Hg (GEM) is rapidly oxidized to Hg(II) compounds, known collectively as reactive gaseous Hg (RGM), in Arctic and Antarctic regions after polar sunrise. The reduction in GEM is correlated with a reduction in surface O(3) concentration, which is thought to be caused by photochemically initiated catalytic reactions involving halogen species, particularly Br and BrO. Initially, the reaction of Hg(0) and BrO to produce HgO and Br was thought to be the dominant reaction, but recent theoretical studies have decisively shown that this reaction is highly endoergic due to the low stability of monomeric gas-phase HgO. This result is in conflict with experimental data on the energetics of the species existing in the vapor over heated HgO (s). One possible explanation for this discrepancy is the existence of highly stable oligomers formed from HgO. Recent high-level quantum calculations on the dimers of HgO and HgS support this concept. In the present work, we systematically examine the structures, stabilities, and other properties of closed (HgX)(n)() ring-type oligomers, n = 2, 3, 4, and 6, X = O, S, as well as infinite one-dimensional (1D) polymers of HgX (studied by using the periodic boundary condition DFT implementation in GAUSSIAN03). We find that the HgX ring oligomers become systematically more stable (per HgX unit) as n increases but that this stability levels off around n = 4-6. We also find that the 1D chain polymers are only marginally more stable than the n = 6 oligomers. To estimate the energies of interaction between the chains in the 3-dimensional (3D) crystal structures of HgX (s), we adopt a cluster model and use the MP2 method to describe the interchain dispersion interactions. We have also obtained optimized geometries for open chain triplets for the dimers, finding them to be substantially more stable than the closed ringlike dimeric species previously described. Trends in relative energies and structures indicate that the higher n oligomers are fairly normal Hg(II) compounds that can be accurately described at low computational levels, as opposed to the monomer and dimer, which possess highly unusual bonding properties and require high-level methods for their description. Nonetheless, even the high n ring, oligomers show close approach of Hg atoms, consistent with a metallophilic-type stabilization. Calculated free energies for the interaction of HgO with H(2)O and with simple models for silicate surfaces are highly favorable, indicating that hydration and surface effects will greatly promote the formation of such species. Molecular cluster models of the HgX surface such as Hg(2)X(XH)(2) are used to calculate the energetics for solvolysis reactions with H(2)O or H(2)S, obtaining good agreement with experiment for the energetics of the dissolution reaction of HgS (s, cinnabar) with H(2)S.

O triclusters revisited: classical MD and quantum cluster results for glasses of composition (Al(2)O(3))2(SiO(2)).

The (17)O NMR spectrum of CaAl(2)Si(2)O(8) glass shows two types of O sites that are not present in the crystalline material. One of these, with (17)O NMR parameters C(Q) = 2.3 MHz and delta = +20 ppm, has been assigned to a "tricluster" O, a local geometry in which the O is coordinated to three tetrahedrally coordinated atoms, either Al or Si. For crystalline CaAl(4)O(7), a tricluster site (with three Al linkages to O, i.e., OAl(3)) has been characterized experimentally, with a C(Q) of 2.5 MHz and a delta of about +40 ppm. Thus, a C(Q) value of 2.5 MHz or less seems to be a characteristic of such sites, although they may show a range of delta values. However, several different quantum chemical cluster calculations employing energy-optimized geometries for various tricluster species have given C(Q) values considerably larger than that seen experimentally in the CaAl(2)Si(2)O(8) glass (with minimum C(Q) values of 3.0 MHz even for all Al species). We have recently shown that for edge-sharing geometries, in which the tricluster O atoms participate in "two-membered rings" of composition Al(2)O(2), the calculated C(Q) values are considerably lower, in the range identified in the glass. However, such two-membered ring geometries had been observed only in crystalline inorganic alumoxanes. Ab initio MD calculations on related compositions, such as the calcium aluminosilicate, CAS, (CaO)(0.21)(Al(2)O(3))(0.12)(SiO(2))(0.67), show a small percentage of O triclusters, but none in two-membered rings of the Al(2)O(2) type, and the calculated C(Q) values for the triclusters that do exist are higher than seen in the original experiments on CaAl(2)Si(2)O(8) glass and not significantly different from those for two-coordinate O in Si-O-Al sites. However, a classical MD simulation of the structure of glassy aluminum silicate AS2, (Al(2)O(3))2(SiO(2)), gave a predominance of O triclusters within two-membered rings, with structures much like those seen in the alumoxanes. We have now calculated (17)O nuclear quadrupole coupling constants and NMR shielding values for clusters extracted from these simulations, using standard quantum chemical methods. The calculated C(Q) values for these O triclusters are now in the range observed experimentally in the CaAl(2)Si(2)O(8) glass (around 2.3-2.6 MHz) when the tricluster O is surrounded by three Al, two of which are part of an Al(2)O(2) ring. This supports the experimentalists' contention that such tricluster O species do exist and have been seen by (17)O NMR.

Calculation of 19F and 27Al NMR parameters for rosenbergite, AlF[F0.5(H2O)0.5]4.H2O, a possible model for Al hydroxyfluorides in solution.

(19)F and (27)Al NMR chemical shifts are calculated for the F and Al atoms of the mineral rosenbergite, AlF[F(0.5)(H(2)O)(0.5)](4).H(2)O The structure of rosenbergite consists of infinite chains of F-corner-sharing Al[F(4)(H(2)O)(2)] octahedra and isolated water molecules. An F-centered molecular cluster of composition Al(2)F(3)(OH(2))(8) (3+) was initially used to model the mineral, with geometries taken both from the two different available x-ray crystal structures and from equilibrium geometries calculated at the 6-31G* B3LYP level (both with and without polarizable continuum solvation). Related Al(F)F(n) em leader clusters, with additional F(-) replacing H(2)O, were also studied. A larger Al-centered cluster model Al(3)F(4)(OH(2))(12) (5+) was also generated from one of the x-ray geometries and produced very similar bridging F shieldings but slightly different Al shieldings. The NMR shieldings were calculated using both HF and B3LYP GIAO methods, with 6-311+G(2df,p) basis sets, and the HF and B3LYP results averaged for the F shieldings as described in previous work. Calculated (19)F NMR shifts (relative to CCl(3)F) using this procedure were within a few ppm of experiment when either set of x-ray crystal structure coordinates was used, but differed by as much as 20 ppm for the energy-optimized geometries. Rosenbergite-like fragments with geometries optimized in water, simulated by a PCM, were used to model Al hydroxyfluoride species in solution. The (19)F NMR shifts for the bridging F atoms in several such model complexes are very similar to those usually attributed to monomeric species such as Al(OH(2))(5)F(2+) in solution, suggesting that the solution species are actually corner bridging oligomers. The F in the monomeric Al(OH(2))(5)F(2+) solution species is too strongly shielded by about 20 ppm to match the experimental peak usually assigned to it.

Calculation of the visible-UV absorption spectra of hydrogen sulfide, bisulfide, polysulfides, and As and Sb sulfides, in aqueous solution.

Recently we showed that visible-UV spectra in aqueous solution can be accurately calculated for arsenic (III) bisulfides, such as As(SH)3, As(SH)2S- and their oligomers. The calculated lowest energy transitions for these species were diagnostic of their protonation and oligomerization state. We here extend these studies to As and Sb oxidation state III and v sulfides and to polysulfides S n 2- , n = 2-6, the bisulfide anion, SH-, hydrogen sulfide, H2S and the sulfanes, S n H2, n = 2-5. Many of these calculations are more difficult than those performed for the As(iii) bisulfides, since the As and Sb(v) species are more acidic and therefore exist as highly charged anions in neutral and basic solutions. In general, small and/or highly charged anions are more difficult to describe computationally than larger, monovalent anions or neutral molecules. We have used both Hartree-Fock based (CI Singles and Time-Dependent HF) and density functional based (TD B3LYP) techniques for the calculations of absorption energy and intensity and have used both explicit water molecules and a polarizable continuum to describe the effects of hydration. We correctly reproduce the general trends observed experimentally, with absorption energies increasing from polysulfides to As, Sb sulfides to SH- to H2S. As and Sb(v) species, both monomers and dimers, also absorb at characteristically higher energies than do the analogous As and Sb(III)species. There is also a small reduction in absorption energy from monomeric to dimeric species, for both As and Sb III and v. The polysufides, on the other hand, show no simple systematic changes in UV spectra with chain length, n, or with protonation state. Our results indicate that for the As and Sb sulfides, the oxidation state, degree of protonation and degree of oligomerization can all be determined from the visible-UV absorption spectrum. We have also calculated the aqueous phase energetics for the reaction of S8 with SH- to produce the polysulfides, S n H-, n = 2-6. Our results are in excellent agreement with available experimental data, and support the existence of a S6 species.

Computing the properties of the copper thioarsenite complex, CuAsS(SH)(OH).

In aqueous solutions in equilibrium with the mineral assemblage CuS (covellite)-Cu(1.8)S (digenite)-Cu(3)AsS(4) (enargite), a copper thioarsenite species, CuAsS(SH)(OH), makes major contributions to both Cu and As solubility (Clarke, M. B.; Helz, G. R. Environ. Sci. Technol. 2000, 34, 1477-1482. The structure and energetics of this complex have been calculated quantum mechanically (Tossell, J. A. Environ. Sci. Technol. 2000, 34, 1483-1488), confirming its high stability and establishing the presence of a novel direct bond between Cu (formally Cu(I)) and As (which is formally As(III) and retains its lone pair). To provide further evidence for the existence of this complex, it would be desirable to concentrate it and to measure its spectral properties. To assist in the confirmation of its identify, we have calculated a number of different spectral properties for this complex, including its vibrational, visible/UV, X-ray absorption near edge (XANES), and Cu and As NMR spectra. The visible/UV spectrum has been calculated using both Hartree-Fock and density functional theory based methods, which have been tested against the known properties of the gas-phase CuCl molecule. We calculate distinctive stretching vibrations of the three-membered Cu-As-S ring around 440-500 cm(-1), an absorption in the visible at around 2.4 eV, and an absorption at low energy in XANES (compared to that calculated for Cu(SH)(2)(-)). The calculated Cu and As NMR properties of CuAsS(SH)(OH) are also distinctive, but both Cu and As are quadrupolar nuclides and their calculated quadrupole coupling constants in CuAsS(SH)(OH) are very large, so their NMR signals may not be observable. Mulliken population analyses, natural bond orbital analyses, and contour plots of HOMO and LUMO electron densities are also used to characterize the bonding within the copper thioarsenite complex. We have also calculated the hydration energy of the complex using polarized dielectric continuum methods, confirming its low degree of stabilization in water.

The effects of hydrolysis and oligomerization upon the NMR shieldings of Be+2 and Al+3 species in aqueous solution.

The 9Be and 27Al NMR shieldings have been calculated for the species Be(OH2)+24, Be(OH2)3OH+1, Be3(OH)3(OH2)+36, Be2(OH)2(OH2)+24, Be2(OH)(OH2)+36, Al(OH2)+36, Al(OH2)5OH+2, and Al2(OH)2(OH2)+48 using a 6-31G* basis set and the gauge-including atomic orbital (GIAO) method. Our results indicate that although hydrolysis deshields the Be and Al nuclei, oligomerization shields them. Since experiment indicates that the most stable Be+2 and Al+3 species in aqueous solution at moderate concentration and pH are Be3(OH)3(OH2)+36 and Al2(OH)2(OH2)+48, respectively, which are both hydrolyzed and oligomerized, their shieldings are little different from those of their unhydrolyzed, unpolymerized parent species Be(OH2)+24 and Al(OH2)+36. The calculated deshielding of Be3(OH)3(OH2)+36 with respect to Be(OH2)+24 is only 0.8 ppm (compared to 0.61 ppm observed experimentally) while the calculated deshielding of Al2(OH)2(OH2)+48 compared to Al(OH2)+36 is 2.1 ppm (compared to 3.5 ppm observed experimentally). The corner sharing Be dimer, Be2(OH)(OH2)+36 is about 0.1 ppm more strongly shielded than Be(OH2)+24. The hydrolyzed monomeric species Be(OH2)3OH+1 and Al(OH2)5OH+2 are calculated to be deshielded by 1.97 and 8.8 ppm, respectively, vs their parent ions. Such species may be observable at very low concentration, but their quadrupole coupling constants are large and they may have large linewidths. Calculated changes in average 1H NMR shieldings for the hydrolyzed, oligomerized species derived from aqueous Be+2 are also in accord with experimental NMR data. Calculated energetics for the formation of oligomeric species from the hydrolyzed ions are consistent with the greater relative stability of oligomerized species in the Be case compared to Al.

Calculation of the Structural, Energetic, and Spectral Properties of Alumoxane and Aluminosilicate "Drum" Molecules.

In aluminosilicate cage compounds Al-O-Al linkages are usually not found, in accord with the "Al avoidance" rule. In some cases Al-O-Al linkages can be stabilized by forming additional bonds to the bridging O atom. This can occur through direct coordination of cations or by the fusing of aluminosilicate rings to create "drum"-like molecules. We have calculated the structures, energetics, and NMR and vibrational spectra for several such aluminosilicate drum-like molecules and for related alumoxanes, as well as for analogous silicate molecules. Calculations on Si(2)Al(4)O(6)H(8), Al(6)O(6)H(6), Si(4)Al(4)O(8)H(12), Si(6)O(9)H(6), Si(8)O(12)H(8), Si(4)Al(4)O(12)H(8)(4)(-), and Si(4)Al(4)O(12)H(8)Na(4) reproduce the experimental structures (where available) and the observed trends in Si NMR shieldings. In the double 3-ring and double 4-ring (D3R and D4R) silicate cages Si(6)O(9)H(6) and Si(8)O(12)H(8) the Si atoms are shielded compared to their monomeric units, with a significantly greater shielding for the D4R compared to the D3R. The Si(4),Al(4) D4R bare anion has about the same Si shielding as Si(8)O(12)H(8), while the neutral Si(4)Al(4)O(12)H(8)Na(4) shows a 13 ppm deshielding. These trends in Si NMR shieldings are in accord with those observed in both the molecules and in aluminosilicate minerals. On the other hand, the fused or "drum"-like D3R and D4R rings show Si atoms and Al atoms which are calculated to be deshielded with respect to their corresponding monomers, in accord with experiment. We also reproduce the difference in frequency of the most intense IR absorptions for the various double-ring molecules. While silicate D4R cages are considerably more stable than corresponding D3R, the stabilities of the D3R molecule Al(6)O(6)H(6) and the hypothetical D4R symmetry Al(8)O(8)H(8) are quite similar. Calculated gas-phase proton affinities for Si(6)O(9)H(6), Si(2)Al(4)O(6)H(8), and Al(6)O(6)H(6) are similar, although protonation causes cage breaking for Si(2)Al(4)O(6)H(8) and Al(6)O(6)H(6). For a drum-like D4R of composition Si(4)Al(4)O(8)H(12), which is calculated to be stable with respect to Si(2)Al(4)O(6)H(8) and Si(4)O(4)H(8), we present a calculated structure as well as NMR properties.

Experimental group B streptococcal infection in the rhesus monkey. I. Disease production in the neonate.

Group B streptococci (GBS) are responsible for serious infections of newborn infants. An experimental model for GBS infection was developed in the newborn rhesus monkey in order to obtain more information concerning the pathogenesis of such infections. A series of 29 newborn monkeys were inoculated with either type Ic or type III GBS or sterile broth. Fatal neonatal meningitis without associated pneumonia was produced consistently following intracerebral inoculation with either type Ic or type III; intracerebral inoculation with sterile broth produced no apparent disease. Variable disease production followed intravenous or intra-amniotic GBS inoculation, and clinical manifestations ranged from no apparent disease to fatal meningitis and pneumonia. This monkey model may be useful for further investigation of treatment and prevention of neonatal GBS infection.

Magnetic transitions observed in sulfide minerals at elevated pressures and their geophysical significance.

The magnetic behavior of iron in chalcopyrite (CuFeS(2)) and pyrrhotite (Fe(7)S(8)) in the pressure range from 1 atmosphere to 20 kilobars has been studied by Mössbauer spectroscopy. Both chalcopyrite and pyrrhotite exhibit transitions from magnetically ordered to disordered states over the range from 5 to 16 kilobars. Both transitions, particularly the loss of ferrimagnetism in pyrrhotite, have geophysical consequences.