Antimicrobial resistance of Streptococcus suis isolates recovered from clinically ill nursery pigs and from healthy pigs at different stages of production

Streptococcus suis isolates (N = 379) from clinically ill pigs and from healthy pigs were tested for antimicrobial susceptibility using a disk diffusion method. Isolates from clinical cases had a higher prevalence of resistance compared with isolates from healthy pigs. There was a high to moderate prevalence of resistance to antibiotics commonly used in nursery pig diets such as tetracycline (84.2%), tiamulin (65.2%), and spectinomycin (40.4%). There was a low prevalence of resistance, however, to antimicrobials that are only used as parenteral treatments and not added to feed (e.g., ceftiofur, florfenicol). These findings should help practitioners in choosing appropriate drugs for use on Ontario swine farms.

An epidemiological study of Streptococcus suis serotypes of pigs in Ontario determined by a multiplex polymerase chain reaction

The purpose of the study was to identify the serotypes of Streptococcus suis from tonsil swabs in clinically ill and healthy pigs in Ontario using a multiplex polymerase chain reaction (PCR) method. Although 22 different serotypes were identified, most isolates were S. suis-like bacteria or untypable.

Anhydro sugar and linkage contributions to circular dichroism of agarose and carrageenan, with conformational implications

The geometry-dependent linkage contributions to the circular dichroism (CD) of agarose and carrageenan were determined by subtracting the monomeric CD from the CD of the polymers. For this purpose, the CD of methyl 3,6-anhydro-alpha-D-galactopyranoside, and of other anhydro sugars, was measured. Application of empirical quadrant rules indicates the observed CD to be that expected for the helical conformations of agarose and carrageenan as derived from diffraction data and modeling calculations. The difference in CD sign in the two polymers arises from a translocation of the beta-D-galactose O-2 atom from one quadrant to the neighboring quadrant of the C-5-O-5-C-1 ether chromophore of the preceding anhydro sugar residue, demonstrating the unusually high spatial resolution of conformational analysis that can be achieved with CD under favorable circumstances.

Experimental chiroptical verification of linkage flexibility in methyl 3-O-(alpha-d-mannopyranosyl)-alpha-d-mannopyranoside

Vacuum UV CD spectra of methyl 3-O-(alpha-D-mannopyranosyl)-alpha-D- mannopyranoside in D2O and as a cast film were obtained in the 145-200 nM region. The disaccharide solution CD per residue is nearly identical to that of the monosaccharide solution CD, and to the monosaccharide film CD. Conversely, the disaccharide film spectrum exhibits a strong positive CD linkage contribution in the 160-170 nm range, which is consistent with the known crystal conformation under the aegis of previously determined sector rules. The close similarity between the monosaccharide and disaccharide solution spectra, therefore, reflects conformational averaging in which the net linkage contribution is approximately zero. The present observation of significant solution linkage flexibility confirms previous conclusions based on optical rotation, as well as conclusions of others based on nmr data. Moreover, when combined with those earlier results, the present work demonstrates the population of at least three distinct potential energy wells on the disaccharide phi,psi potential energy surface.

Vacuum ultraviolet circular dichroism of gellan-family polymer films from water and dimethyl sulfoxide

The denaturing effect of dimethyl sulfoxide (Me2SO) on the conformation of the gellan-welan-rhamsan family of microbial polysaccharides is directly demonstrated by circular dichroism (CD). The three polysaccharides display strikingly similar CD spectra (140-210 nm) for films cast from Me2SO. The disrupting effect of Me2SO on gellan and welan conformations has previously been reported by others on the basis of light-scattering and viscosity studies. Films cast from aqueous solutions at room temperature show more-intense CD bands, both at 182 nm, as is also observed for aqueous solutions, and in the 150-175 nm region. These features correspond to the ordered helical chains found by X-ray diffraction studies of similarly prepared films.

A conformational study of agarose by vacuum UV CD

Agarose films were prepared using a variety of casting conditions, heat treatments, and solvation treatments. Films represented the high temperature sol, the room temperature gel, and a high temperature state with cross-links intact. The vacuum uv CD of the film samples varies considerably, but the similarities between the film CD and the previously reported solution CD show that dehydration per se does not affect the CD. Combining the CD results for the dried sol with the x-ray results of Foord and Atkins leads to a description of the high temperature sol in terms of locally extended chain conformations. The CD of the gel and its peculiarly high uv absorption are satisfactorily, albeit not uniquely, interpreted in terms of the double-helix model of the gel, in agreement with previous conformational studies based on chiroptical properties.