EN
The aim of the paper was to present the clinical data in four cases of flavobacteria infections in fish cultured in Poland and to characterize the isolates. The cases occurred in September 2005 and in February and March 2006 in three trout farms and one carp farm. In the first case, Fl. psychrophilum and Fl. columnare were isolated from apparently healthy rainbow trout. In the second case, common carp showed clinical signs specific for columnaris disease and abundant growth of bacteria producing yellow colonies was observed in skin and gills samples. The bacteria of separated isolates were identified as Fl. columnare. In the third case, abundant growth of flavobacteria was obtained from rainbow trout fry population with haemorrhages in the yolk sac and numerous mortalities. Separated isolates were identified as Fl. psychrophilum and Fl. branchiophilum. In the fourth case, skin darkening and mortalities were observed in rainbow trout after moving to another farm. An abundant growth of bacteria from kidney and intestine samples was obtained and yellow colonies grew uniformly or predominated over other bacterial flora. Fl. psychrophilum was identified among the isolates. In total, 17 isolates were identified. All the isolates showed characteristics specific for flavobacteria: they grew on Cytophaga agar, produced yellow colonies with spreading, wrinkled or whole edges (dependend on bacteria species). Cultures comprised Gram-negatie, long cells without spores or fruiting bodies (except for three isolates). Other phenotypic properties were consistent with those of reference strains used in the studies. The isolates identified as Fl. columnare, Fl. branchiophilum or Fl. psychrophilum varied little in their range of properties with regard to data of other authors.