Characterization by restriction endonuclease analysis and DNA hybridization using IS900 of bovine, ovine, caprine and human dependent strains of Mycobacterium paratuberculosis isolated in various localities.

DNA of 90 mycobactin-dependent strains of Mycobacterium paratuberculosis, isolated in 9 countries, was digested with restriction endonuclease PstI and hybridized with a DNA fragment containing insertion sequence IS900. Bovine strains (n = 73) were isolated from 61 animals in 17 herds, ovine strains (n = 15) from 13 animals in 3 herds and the set was completed by 1 caprine and 1 human (Linda) strain. Three types, tentatively designated A (n = 37), B (n = 51) and C (n = 2) were differentiated by restriction fragment length polymorphism (RFLP). Of the bovine strains 27, 45 and 1 were classified as belonging to types A, B and C, respectively; of the 15 ovine strains 10 and 5 belonged to types A and B, respectively; the caprine strain belonged to type C. The human strain Linda, isolated in the U.S.A., from a man with Crohn's disease, belonged to B type. A certain degree of type uniformity was observed among strains isolated within one herd in the course of several years, and the prevalence of a single type was also recorded within individual regions of the Czech Republic and Slovakia. Type A was identified in the course of 2 years in a sheep farm with frequent sales and purchases of animals, and type C was demonstrated in a goat kept in the same farm. Differences between RFLP types of the strains isolated from mesenteric lymph nodes and intestinal mucosa were found in one cow and one sheep. Selected strains of M. paratuberculosis RFLP type A (14 strains) and B (18 strains) were digested with restriction endonuclease BstEII. All the strains of A type were classified into C1 group and all the strains of B type into Cx group.

[Fluorometric evaluation of aflatoxigenic strains of the molds Aspergillus flavus and Aspergillus parasiticus after culture in liquid medium]. / Fluorometrické hodnocení aflatoxinogenity kmenu plísne Aspergillus flavus a Aspergillus parasiticus po kultivaci v tekutém médiu.

The production of aflatoxin (AF) by A. flavus and A. parasiticus strains originating either from the Czechoslovak collection or isolated from feed mixtures and from peanut samples was determined following their cultivation in liquid synthetic GV medium. Their aflatoxicogenic effects were estimated from fluorescence of the GV medium after its application onto filter paper or by determining emission intensity of chloroform extracts of the medium in a fluorescence spectrophotometer. In extracts with emission intensity from 0 to 880 at two sensitivity settings of the device, AFB1 concentration was found to be in the range from 0 to 54.5 mg.l-1 when determined by means of the RIA method. Emission intensity was not in a linear relationship with AFB1 level in the medium and was higher than at a corresponding concentration of AFB1 standard solution. The fluorometric method is many times more sensitive than visual assessment of medium fluorescence on filter paper, which, for its part, was more reliable than the estimation of fluorescence following the cultivation of strains with low AF production on solid APA medium. This and other screening methods are surpassed by the employed fluorometric method as far as the sensitivity and saving of time are concerned, especially when medium extract is used for further more precise analysis.