CHARACTERIZATION OF TOXIGENIC <i>Enterobacteriaceae </i> FROM FARM ANIMALS WITH GASTROINTESTINAL DISEASES
In most Enterobacteriaceae family bacteria, being the main etiological agents of the diseases in young farm animals, there is no strict correlation between a serological group and toxic activity. Thus, when diagnosing the diseases, a direct identification of the bacterial adhesins or the toxin detection with the laboratory animals are conducted, and of these two procedures the animal test is usually long and difficult. We evaluated toxins and virulence in the pathogenic and opportunistic bacteria isolated from 1-5 days Holstein and Black Mottled calves with the diarrhea syndrome, and in the reference strains using different tests with the laboratory animals (white mice, the Self line guinea pigs, Chinchilla rabbits, and quail Coturnix comuni ). Most of the samples (64 of 86 isolates) were identified as Escherichia coli. In 34 E. coli isolates the O-antigen was not detected. In the test on white mice, infected intraperitoneally with a bacterial suspension, 35.0 % and 65.0 % of the bacteria were identified as pathogenic and nonpathogenic, respectively. Nevertheless, the toxins were detected in 53.9 % of the studied isolates and reference strains of Salmonella (2 strains), Klebsiella (2 strains), Kluyvera (a strain), Yersinia (3 straines), Escherichia (13 strains) genera. Moderate and low toxic properties were identified in 15.4 % and 38.5 % of these isolates, respectively, and in 46.1 % no toxigenic activity was found. By the histochemical methods, the histomorphological changes in tissues and organs of the laboratory animals were revealed under the experimental toxicoinfection caused by Enterobacteriaceae. At experimental toxemia, induced by E. coli and Y. pseudotuberculosis strains, a hydropic dystrophy of the villus epithelium cells developed in the small intestine, and a generalized microvascular reaction occurred in the gastric mucosa and in the mucosa of small and large intestines.