Staphylococcus aureus in the nose and throat of Iowan families.

The study objective was to determine the prevalence of Staphylococcus aureus colonisation in the nares and oropharynx of healthy persons and identify any risk factors associated with such S. aureus colonisation. In total 263 participants (177 adults and 86 minors) comprising 95 families were enrolled in a year-long prospective cohort study from one urban and one rural county in eastern Iowa, USA, through local newspaper advertisements and email lists and through the Keokuk Rural Health Study. Potential risk factors including demographic factors, medical history, farming and healthcare exposure were assessed. Among the participants, 25.4% of adults and 36.1% minors carried S. aureus in their nares and 37.9% of adults carried it in their oropharynx. The overall prevalence was 44.1% among adults and 36.1% for minors. Having at least one positive environmental site for S. aureus in the family home was associated with colonisation (prevalence ratio: 1.34, 95% CI: 1.07-1.66). The sensitivity of the oropharyngeal cultures was greater than that of the nares cultures (86.1% compared with 58.2%, respectively). In conclusion, the nares and oropharynx are both important colonisation sites for healthy community members and the presence of S. aureus in the home environment is associated with an increased probability of colonisation.

Triangular kinetic schemes applied to the stability of a heme-globin complex.

Horse heart apomyoglobin traps the heme released from Aplysia californica myoglobin. The kinetics fit a triangular mechanism for a bipbasic reaction. Laplacian solutions for differential equations appropriate to triangular kinetic schemes involving up to four rate constants are elaborated and confirmed. Two general schemes and two special cases are considered. In the first scheme, a rearrangement of the starting material is concurrent with product formation. In the second scheme, the starting material forms two products in equilibrium at two different rates. A general equation for the absorbance-time curve is derived for these triangular schemes, from which rate constants can be estimated. Changes in instantaneous rate versus time are employed to analyze the absorption versus time plots and the curvature of a first-order rate analysis. Aplysia metmyoglobin equilibrates between slow donor (pentacoordinate, which lacks the axial water molecule) and fast donor (bexacoordinate). No heme release was observed for deoxy, oxy, carbonyl, or azide derivatives of the Aplysia myoglobin, or when the distal HisE7 of the apohemoprotein is replaced by leucine or valine. This suggest a role for hydrophobicity of the active site, and for a trans effect of the axial ligand in determining the stability of the embedded prosthetic heme.

Iron ligand recognition by monomeric hemoglobins.

Binding affinities of monomeric Glycera dibranchiata hemoglobin for some anions and heterocyclic amines, including imidazoles, pyrazole, triazole and tetrazole have been evaluated and compared with those of sperm whale and horse heart myoglobin. The proteins' affinities for substituted heterocyclic amines are strongly influenced by the steric bulk and flexibility of the aromatic ring. The ligand coordination mode depends on the heme oxidation state, iron(III) amine adducts being more stable than the iron(II) adducts, the higher affinities of stronger Brønsted-Lowry bases reflecting their essentially sigma-donor character. The bifunctional molecule morpholinoethylisocyanide acts as a redox-state-dependent ambidentate ligand, binding as an N-donor to iron(III), but as a C-donor to iron(II). pH-Dependences of the ESR and optical spectra of the azole adducts reveal iron-linked ionisations and spin-equilibria in the heme pocket. Enthalpy and entropy changes for the binding process were estimated for several ligands, and mutually compensatory behaviour is observed globally for delta H degree and delta S degree. At the compensation temperature theta, the binding affinities of monomeric Glycera dibranchiata hemoglobin and sperm whale myoglobin are similar and associated with free energy changes delta G degree (theta) approximately -9 +/- 1 kJ mol-1 for the heterocyclic and anionic ligands.