Sundell, From genotype to phenotype - Diversity and population structure of Flavobacterium psychrophilum

This thesis integrates the tools of molecular genetics and conventional phenotypic microbiology to bring increased knowledge about the diversity and population structure of the fish pathogenic bacterium Flavobacterium psychrophilum. This work shows that the pathogen has an epidemic structure dominated by one particular globally distributed genetic lineage containing specific genotypes associated with high mortalities in economically important salmonid fish species. The simultaneous presence of genetically divergent clones and the observed population heterogeneity within disease outbreaks, however, present a challenge for disease control. Antimicrobial resistance was strongly associated with outbreak strains and evidence indicating dissemination of harmful strains eith commercial movement of fish and fish eggs is strengthened.