Genetic and virulence characterization of Flavobacterium columnare from channel catfish (Ictalurus punctatus).
OBJECTIVE
To develop a method for conducting pulsed-field gel electrophoresis (PFGE) on Flavobacterium columnare, to use PFGE to characterize F. columnare channel catfish isolates, and to determine whether variation in pathogenic potential exists in F. columnare isolates from channel catfish.


RESULTS
On the basis of PFGE-derived profiles, similarity dendrograms constructed for more than 30 F. columnare isolates showed two major genetic groups with more than 60% similarity. Channel catfish fingerlings challenged with PFGE group A isolates by bath immersion had significantly higher average mortalities (>60%) than fish challenged with PFGE group B isolates (<9%). However, abrasion and skin mucus removal made channel catfish fingerlings susceptible to disease caused by group B isolates following immersion exposure.


CONCLUSIONS
Our results suggest that two genetic divisions of F. columnare channel catfish isolates exist, and that isolates in PFGE group A isolates tend to be more pathogenic to immunocompetent channel catfish fingerlings than PFGE group B isolates.


CONCLUSIONS
PFGE is a potentially useful tool for determining whether F. columnare isolates are more likely to be primary or secondary pathogens. Pathogenesis research for columnaris disease in catfish should focus on pathogenic isolates from PFGE group A.
Soto
E
E
Thad Cochran National Warmwater Aquaculture Center, Stoneville, MS, USA.
Mauel
M J
MJ
Karsi
A
A
Lawrence
M L
ML
D000818:Animals; D017756:Aquaculture; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000032:analysis; D016521:Electrophoresis, Gel, Pulsed-Field / Q000379:methods; D005393:Fish Diseases / Q000382:microbiology; D045826:Flavobacteriaceae Infections / Q000382:microbiology; D005417:Flavobacterium / Q000235:genetics* / Q000472:pathogenicity*; D005516:Food Microbiology; D007059:Ictaluridae / Q000382:microbiology*; D008922:Mississippi; D014774:Virulence
D004269:DNA, Bacterial