Thirty-eight strains, representative of 575 Escherichia coli isolates from weaned diarrheic rabbits, were tested for their ability to adhere in vitro to rabbit intestinal villi and to HeLa 229 cells. The O103 rhamnose-negative, highly pathogenic strains, which are epidemiologically predominant in France, attached to intestinal villi prepared from 8-day-old as well as 6-week-old rabbits and gave a diffuse adhesion pattern with HeLa cells. These adhesion properties were associated with the presence of a protein with a molecular weight of 32,000 in surface extracts of the strains. The expression of the adhesion was dependent on culture medium and temperature, and the adhesion was D-mannose resistant. Antisera raised against the 32,000-molecular-weight protein inhibited adhesion. This adhesion was not expressed in two nonpathogenic O103 strains, indicating its implication in virulence. However, the same adhesin was expressed by two O128 non- or moderately pathogenic strains. Therefore, adhesion to enterocytes is not the only factor involved in the pathogenicity of O103 strains.

A total of 575 Escherichia coli strains isolated from weaned rabbits experiencing diarrhea in 119 French commercial farms were tested for 0 serogroups. The results showed a strong predominance of serogroup 0103 strains. A sample of 126 strains were further checked for simplified biotypes by using five carbohydrate fermentation reactions. Of 72 0103 strains, 70 were shown to belong to biotypes characterized by a rhamnose-negative reaction. Four of nine serogroup 068 strains also showed this type of reaction. Thirty-nine strains, representative of the sérotypes and biotypes found, were further tested for experimental pathogenicity in weaned rabbits and for antibiotic susceptibility. All the rhamnose-negative strains produced life-threatening watery or hemorrhagic diarrhea, whereas rhamnose-positive strains induced only mild diarrheic syndrome without any mortality or no clinical signs at all. Rhamnose-negative, highly pathogenic strains did not belong to related antibiotypes. We think that O serogrouping together with biotyping, or even rhamnose fermentation testing, may be an important clue in the diagnosis of enteropathogenic strains from rabbits in France, permitting rapid identification of highly pathogenic strains and leading to improved prognosis and treatment.

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The toxic effect of various doses of ochratoxin A on the rat testis was investigated after a single intratesticular injection. At time of sacrifice (day 10) degenerating changes occur in the testicular tissues: seminiferous tubules dilatation, cytolysis of the seminiferous epithelium, hyperplasia of the interstitial tissue, vascular thrombosis. The relations between the blood supply disturbances and the observed lesions are discussed.