Isolation, serotypes, and virulence-associated properties of Yersinia enterocolitica from the tonsils of slaughter hogs.

The objectives of this study were to determine the carriage rate of Yersinia enterocolitica in the tonsils of slaughter hogs, and to characterize them with regard to phenotypic and virulence-associated properties. Of 202 pigs examined from an abattoir in Prince Edward Island, 85 were culture positive for Y. enterocolitica. Sixty-seven percent of isolates belonged to serotype O:3, and 20% were serotype O:5. All isolates produced urease and 95% of O:3 isolates showed virulence-associated characters of autoagglutination at 37 degrees C and lack of fermentation of esculin and salicin. All isolates were tested for crystal violet binding, calcium dependency, and virulence plasmids. Eight isolates (5 belonging to serotype O:3, 2 belonging to O:5,27, and 1 belonging to O:7,8) were tested in addition for the production of heat-stable enterotoxin (ST), and iron-chelating siderophores. Of the 57 O:3 isolates, 93% were positive for crystal violet binding and calcium dependency and 98% possessed a 40-45 MDa plasmid. Four of the 5 O:3 isolates tested for ST related to Escherichia coli STa in a commercial enzyme immunoassay were positive. Six of the 8 isolates belonging to 3 different serotypes produced large orange halos around the colonies on a chrome-azurol-s agar assay medium, for siderophores. Antimicrobial susceptibility tests of all 85 isolates against 16 drugs showed 100% susceptibility against 12 drugs, including trimethoprim-sulfamethoxazole and tetracycline.

Skin-tumor-initiating ability of benzo(a)pyrene-7,8-diol-9,10-epoxide (anti) when applied topically in tetrahydrofuran.

The skin-tumor-initiating abilities of various metabolites of benzo(a)pyrene (BP) were determined in mice by using a two-stage system of tumorigenesis. We previously reported that BP-7,8-dihydrodiol (+/- trans) was approximately as potent as BP, suggesting that it may be a proximate carcinogen, but the alleged ultimate carcinogen of BP [BP-7,8-dihydrodiol-9,10-epoxide (anti)] was a weak tumor initiator (Cancer Lett.2: 115, 1976). Because of its high reactivity, the tumor-initiating ability of the BP-7,8-dihydrodiol-9,10-epoxide (anti) was determined by using acetone, benzene, and tetrahydrofuran (THF) as the solvent vehicles. The 'diol-epoxide' of BP was found to be an effective tumor initiator when applied topically in THF. The effectiveness of the various vehicles for the 'diol-epoxide' was as follows: THF greater than benzene greater than acetone; however, acetone was the best solvent for BP tumor initiation. The BP-9,10-dihydrodiol and BP-3-hydroxy were found to be weak tumor initiators. BP-3-hydroxy was also tested for tumor-promoting ability and was found to be inactive in this capacity.