ARS | Publication request: Host-specific association between Flavobacterium columnare genomovars and fish species

Submitted to: Systematic and Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 16, 2007
Publication Date: December 6, 2007
Repository URL: http://handle.nal.usda.gov/10113/12364
Citation: Olivares-Fuster, O., Baker, J.L., Terhune, J.S., Shoemaker, C.A., Klesius, P.H., Arias, C.R. 2007. Host-specific association between Flavobacterium columnare genomovars and fish species. Systematic and Applied Microbiology. 30: 624-633.

Interpretive Summary: Flavobacterium columnare is an important gram-negative bacterial pathogen of farm raised channel catfish. In previous studies we demonstrated two genetic types (Genomovar I and Genomovar II) using bacteria obtained from cases submitted to diagnostic laboratories throughout the southeast. Most research suggests that this bacterium is present on fish and in the aquatic environment and can be transferred through the water. However, limited information is available on the presence of this aquatic bacterium in the natural environment (i.e. rivers). This study demonstrated the presence of Flavobacterium columnare in a river environment and that the two genetic types were present. Genomovar II was more associated with catfish, whereas, Genomovar I was associated with threadfin shad.

Technical Abstract: 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.