DAO 96:221-227 (2011)  -  DOI: https://doi.org/10.3354/dao02371

ABSTRACT: The adhesion dynamics of Flavobacterium columnare to fish tissues were evaluated in vivo by immersion challenge followed by bacterial plate count and confirmatory observations of gill-adhered bacterial cells using scanning electron microscopy. Adhesion of F. columnare genomovar I (ARS-1) and II (BGFS-27) strains to skin and gill of channel catfish Ictalurus punctactus and gill of zebrafish Danio rerio was compared. At 0.5 h post-challenge, both strains adhered to gill of channel catfish at comparable levels (10⁶ colony forming units [CFU] g^–1), but significant differences in adhesion were found later in the time course. Channel catfish was able to effectively reduce ARS-1 cells on gill, whereas BGFS-27 persisted in gill beyond the first 24 h post-challenge. No significant difference was found between both strains when adhered to skin, but adhered cell numbers were lower (10³ CFU g^–1) than those found in gill and were not detectable at 6 h post-challenge. Adhesion of BGFS-27 cells to gill of zebrafish also occurred at high numbers (>10⁶ CFU g^–1), while only <10² CFU g^–1 of ARS-1 cells were detected in this fish. The results of the present study show that particular strains of F. columnare exhibit different levels of specificity to their fish hosts and that adhesion to fish tissues is not sufficient to cause columnaris disease

KEY WORDS: Adhesion · Columnaris disease · Flavobacterium columnare · Host–pathogen ­specificity