Demonstration of R factors in Bordetella bronchiseptica isolated from pigs

Transferability of drug resistance in strains of Bordetella bronchiseptica isolated from pigs was examined. These strains were resistant to sulfadimethoxine (SA, more than 1,600 mug/ml), streptomycin (SM, more than 800 mug/ml), and aminobenzyl penicillin (APC, 200 mug/ml). All of them could transfer their drug resistance as one unit to a sensitive strain of Escherichia coli as well as to B. bronchiseptica by mixed cultivation. The transferred SM-SA-APC resistance in the exconjugants of E. coli and B. bronchiseptica was also transmissible by mixed cultivation. But the transfer of triple resistance was not mediated by the cell-free filtrate of the drug-resistant strain of B. bronchiseptica which was used as donor. The triple resistance in the exconjugant E. coli ML1410 was found to be eliminated as a whole by treatment with acriflavin. According to these results, it could be safely concluded that R factors carrying SM-SA-APC resistance were demonstrated in strains of B. bronchiseptica isolated from pigs.

Molecular Weight Dependence of Relaxation Spectra of Amorphous Polymers in the Rubbery Region. VII. Comparisons of Experimental Relaxation Spectra with Those Estimated from Molecular Weight Distributions

In a previous paper, the relationship between the relaxation spectrum of an amorphous high polymer in the rubbery region and the molecular weight distribution function was studied by the phenomenological theory method. We found a simple, direct proportional relationship between them. The reliability of assumptions and approximations made for the theoretical study can be evaluated by comparison of calculated and experimental data. As reported previously, selection of values for the simplified method was optional in calculating molecular weight dependence of the relaxation spectrum of a sample with a homogeneous distribution. Therefore, the feasibility of selection has to be evaluated by comparison of calculated results with observed data. For the comparison, it is necessary to obtain experimental data for a sample having a homogeneous distribution and compare it with calculated results for the relaxation spectrum and molecular weight distribution of the previous paper. However, these data are scarce in the current literature. From available past literature, we selected polystyrene, poly(vinyl acetate) and polyisobutene as typical samples of amorphous high polymers. In addition, experimental data for two samples of polystyrene were included. Thus, data for a total of five samples were compared with calculated results of the previous paper.