Isolation of aCarnobacterium maltaromaticum-like bacterium from systemically infected lake whitefish (Coregonus clupeaformis)

Abstract

Herein we report on the first isolation of a Carnobacterium maltaromaticum-like bacterium from kidneys and swim bladders of lake whitefish (Coregonus clupeaformis) caught from Lakes Michigan and Huron, Michigan. Isolates were Gram-positive, nonmotile, facultatively anaerobic, asporogenous rods that did not produce catalase, cytochrome oxidase, or H2S, and did not grow on acetate agar. Except for carbohydrate fermentation, many phenotypic characteristics of lake whitefish isolates coincided with those of C. maltaromaticum, the causative agent of pseudokidney disease. Partial sequencing of 16S and 23S rRNA genes, as well as the piscicolin 126 precursor gene, yielded 97% and 98% nucleotide matches with C. maltaromaticum, respectively (accession numbers EU546836 and EU546837; EU643471). Phylogenetic analyses showed that lake whitefish isolates of this study are highly related, yet not fully identical to C. maltaromaticum. The presence of the C. maltaromaticum-like bacterium was associated with splenomegaly, renal and splenic congestion, and thickening of the swim bladder wall with accumulation of a mucoid exudate. Examination of stained tissue sections revealed renal and splenic congestion, vacuolation and bile stasis within the liver, and hyperplasia within the epithelial lining of the swim bladder. The concurrent presence of pathological changes and the C. maltaromaticum-like bacteria suggests that this bacterium is pathogenic to lake whitefish.

Carnobacterium maltaromaticum infections in feral Oncorhynchus spp. (Family Salmonidae) in Michigan

“…This goes side by side with our previous study on lake whitefish (Loch et al, 2008), which found that Carnobacterium infection prevalence in Lake Huron stocks was lower than infection prevalence observed in Lake Michigan stocks. On a year by year basis, Carnobacterium infection prevalence varied significantly, being highest in 2005, dropping off in 2006, and then increasing in both of the following years.…”

“…Thus, this character is quite variable among different strains of C. maltaromaticum. Other biochemical characteristics, such as acid production from mannitol and inulin, which have classically been used to dichotomize members of the genus Carnobacterium (Montel et al, 1991;Holt et al, 2000), showed intra-species variation in this study, as well as in the studies of Hiu et al (1984), Baya et al (1991), Starliper et al (1992), and Loch et al (2008) and continue to hamper definitive identifications that rely solely on phenotypic and biochemical schemes. The current study further substantiates this point and is epitomized by strain Cm 10 of this study, which was identified as C. divergens phenotypically but definitively identified as C. maltaromaticum through molecular and phylogenetic analysis, while the opposite was true for C. maltaromaticum strain Cm23, a matter that underscores the importance of genetic approaches in the definitive identification of Carnobacterium spp.…”

“…For example, C. maltaromaticum ATCC strain 27865 (originally retrieved from raw milk) and the strains of this study were different in their ability to produce acid from sorbitol (Table 2). A lack of acid production from sorbitol is reported in the original description of C. piscicola (now C. maltaromaticum) by Hiu et al (1984) and Austin and Austin (2007), and was also reported for the Carnobacterium strains recovered from lake whitefish by Loch et al (2008); however, 93% of the C. maltaromaticum isolates recovered in this study were sorbitol positive, while Baya et al (1991), Starliper et al (1992), Toranzo et al (1993), and Lai and Manchester (2000) reported either a positive or a weak/ delayed positive reaction for sorbitol. Thus, this character is quite variable among different strains of C. maltaromaticum.…”

“…stocks in Michigan. Other than our previous report on the distribution of C. maltaromaticum in lake whitefish and its potential role in causing pathological lesions (Loch et al, 2008), reports on this infection in other fish species residing in the Great Lakes basin is lacking. An unexpected finding of this study was that while C. maltaromaticum infections were present in both diseased and apparently healthy captive rainbow trout as previously reported, this bacterium was even more prevalent in feral salmon stocks.…”

Meningoencephalitis Associated With Carnobacterium maltaromaticum–Like Bacteria in Stranded Juvenile Salmon Sharks (Lamna ditropis)

“…1 A C. maltaromaticum-like bacterium was isolated in association with histological abnormalities in lake whitefish (Coregonus clupeaformis) from Lakes Michigan and Huron. 12 In support of the role of C. maltaromaticum as a fish pathogen, Leisner et al 10 identified specific genes in the C. maltaromaticum genome encoding virulence factors. Although members of the genus Carnobacterium are not considered human pathogens, they have been recovered from wounds and blood cultures in human patients.…”