Investigation of Surface Structure Diversity of Isolates of Flavobacterium branchiophilum from Ontario, Canada

Abstract

Flavobacterium branchiophilum is the etiological agent of bacterial gill disease (BGD). As little was known about cell surface structures of F. branchiophilum, the lipopolysaccharide and capsular serotype diversity of 12 strains isolated from cases in Ontario, Canada were investigated. The study shows F. branchiophilum produces low molecular weight lipopolysaccharides containing short O-antigens or lipooligosaccharides and high molecular weight capsular polysaccharides. Low molecular weight epitopes were extensively cross-reactive while high molecular weight epitopes were more antigenically diverse. A serotyping scheme using polymers of this organism was proposed. Examination of F. branchiophilum cells by an indirect fluorescence antibody technique demonstrated that antigenic surface molecules were evenly distributed. In addition, pili-like structures and capsular halos could be observed on the entirety of the cell by transmission electron and immunoelectron microscopy. Overall, the study shows novel findings and generated results that can be used toward understanding the role of F. branchiophilum antigenic surface structures.