Genome-wide comparison ofCarnobacterium maltaromaticumderived from diseased fish harbouring important virulence-related genes

Abstract

AlthoughCarnobacterium maltaromaticumhas been used as a probiotic in fish, it was reported to cause disease for the first time in Korea. The objective of this study was to understand the differences between pathogenic and non-pathogenic strains. Pathogenicity was tested by challenging rainbow trout withC. maltaromaticumATCC35586 and 18ISCm isolated from diseased fish, and DSM20342 isolated from a dairy product. We also compared 24 genomes ofC. maltaromaticumstrains plus the genome of our isolate 18ISCm sequenced in this study. Only the strains from diseased fish caused high mortality with severe histopathological changes. Although all strains shared more than 90% of Ko_id,wecCandxtmAwere found only in strains from diseased fish. Interestingly, only strains from diseased fish harboured twowecCparalogs involved in the production of D-mannosaminuronic acid which is a major component of a well-known virulence factor, teichuronic acid. TwowecCparalogs of 18ISCm were increased when they were co-cultured with trout blood cells, suggesting thatwecCgenes might play a role in virulence. The results of this study show that strains isolated from diseased fish are different from strains derived from food in terms of pathogenicity to fish and the presence of virulence-related genes.