A proposed serotyping system for Flavobacterium psychrophilum

Aims: To develop a common serological system for rapid and routine identification of the fish pathogen Flavobacterium psychrophilum . Methods: Thirty-four isolates of Fl. psychrophilum from different fish species and different geographical areas were typed using a slide agglutination test and an enzyme-linked immunosorbent assay (ELISA). Results: Seven host-dependent serovars (1: salmon; 2: trout; 3: trout; 4: eel; 5: carp; 6: tench; 7: ayu) were found. Serovar 2 was divided into two antigenic subgroups (2a and 2b). The results achieved by both slide agglutination and ELISA methods were totally consistent with each other. Although both techniques proved to be simple to carry out and useful, only the ELISA allowed identification of Fl. psychrophilum serovars using unabsorbed antiserum and whole-cells as antigens. Significance and Impact of the Study: This paper proposes a harmonized scheme for serological identification of Fl. psychrophilum to be used for diagnostic and seroepidemiological studies of the diseases it causes.