Host-specific association between Flavobacterium columnare genomovars and fish species

A total of 90 Flavobacterium columnare isolates were recovered from predominant wild fish species in the Mobile River, Alabama, USA. Isolates were identified and confirmed by fatty acid methyl ester analysis and specific PCR amplification. Genomovar ascription was performed using 16S-restriction fragment length polymorphism (RFLP) analysis. The majority of genomovar I isolates were recovered from threadfin shad while genomovar II isolates came from catfish (including channel and blue catfish). Additional genotyping methods, including multilocus sequence analysis (MLSA), internal spacer region-single strand conformation polymorphism analysis (ISR-SSCP) and amplified fragment length polymorphism (AFLP), confirmed a clear division of the isolates into two groups that matched genomovar ascription. Fingerprinting methods revealed a higher genetic diversity within genomovar II isolates. Our data confirmed the coexistence of F. columnare genomovars I and II in a natural environment. A statistically significant association between genomovar I and threadfin shad was demonstrated while genomovar II strains were mainly recovered from catfish species.