PubMed · 13652775
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D KASSAY, Z LABAS. 1959. A study on intersegmental septa.. https://doi.org/10.1378/chest.35.6.625
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Reported here is an unusual cluster of non-invasive infections caused by an emm28 Streptococcus pyogenes strain resistant to bacitracin, erythromycin and clindamycin detected in Santander, Spain. Since one of the characteristics of group A streptococci is their almost uniform susceptibility to bacitracin, this finding was unusual, and a search for bacitracin-resistant Streptococcus pyogenes strains was conducted in two other distant cities of Spain (Madrid and San Sebastián) where their presence was confirmed. These strains were frequently associated with erythromycin- and clindamycin-resistance, and most of them belonged to a unique emm28 T28, ST52 clone.
A new, simple and accurate micellar electrokinetic chromatography (MEKC) method is established for quantification of hydrocortisone, polymyxin B and Zn-bacitracin in local pharmaceutical preparations. The separation was carried out at 25 degrees C and 25 kV, using a 15 mmol L(-1) phosphate-15 mmol L(-1) borate buffer (pH 8.2), 60 mmol L(-1) sodium dodecylsulfate (SDS), and 10% methanol-water (v/v) as background electrolyte. Under these conditions the analysis takes about 23 min. The method has been applied for quantifying these compounds in two different commercial pharmaceutical products and the method gave good results when compared with a reference spectrophotometric multivariate calibration method.
Binding of Zn(2+) to bacitracin A(1) was studied by capillary electrophoresis in water/2,2,2-trifluoroethanol (70/30 v/v) at different apparent pH values in order to estimate the association constant of metal, the acidic dissociation constants and the Stokes radii of both free and bounded peptide in apolar environment. The Stokes radii of the free peptide species were compared with those in aqueous solution, as obtained in a recent study performed by our group, indicating that apolar environment stabilizes bacitracin A(1) in a conformational structure with the lateral chain of apolar amino acids exposed on the external surface. This conformation of the macrocyclic dodecapeptide is ready to interact with Zn(2+) ion, as pointed out by the strong increase of the association constant measured in water/2,2,2-trifluoroethanol with respect to the value obtained in aqueous solution. In addition, whereas Zn(2+) ion binding in aqueous solution provides a sensible reduction of peptide Stokes radius, no sensible variations following to ion binding were observed in hydro-organic solution. The present results suggest that the apolar environment, rather than the metal ion binding, could be responsible for the conformational transition that brings bacitracin A(1) towards its biologically active structure.*