Characterization of spaC‐type Erysipelothrix sp. isolates causing systemic disease in ornamental fish

Abstract

Since 2012, low-to-moderate mortality associated with an Erysipelothrix sp. bacterium has been reported in ornamental fish. Histological findings have included facial cellulitis, necrotizing dermatitis and myositis, and disseminated coelomitis with abundant intralesional Gram-positive bacterial colonies. Sixteen Erysipelothrix sp. isolates identified phenotypically as E. rhusiopathiae were recovered from diseased cyprinid and characid fish. Similar clinical and histological changes were also observed in zebrafish, Danio rerio, challenged by intracoelomic injection. The Erysipelothrix sp. isolates from ornamental fish were compared phenotypically and genetically to E. rhusiopathiae and E. tonsillarum isolates recovered from aquatic and terrestrial animals from multiple facilities. Results demonstrated that isolates from diseased fish were largely clonal and divergent from E. rhusiopathiae and E. tonsillarum isolates from normal fish skin, marine mammals and terrestrial animals. All ornamental fish isolates were PCR positive for spaC, with marked genetic divergence (<92% similarity at gyrB, <60% similarity by rep-PCR) between the ornamental fish isolates and other Erysipelothrix spp. isolates. This study supports previous work citing the genetic variability of Erysipelothrix spp. spa types and suggests isolates from diseased ornamental fish may represent a genetically distinct species.

Genomic and Immunogenic Protein Diversity of Erysipelothrix rhusiopathiae Isolated From Pigs in Great Britain: Implications for Vaccine Protection

“…It was previously suggested that Spa proteins are likely important virulence factors associated with the pathogenic potential of E. rhusiopathiae in comparison to the less pathogenic E. tonsillarum (To and Nagai, 2007), and until recently, no Spa-related genes or proteins had been found in E. tonsillarum (To and Nagai, 2007;Shen et al, 2010). To our knowledge, the occurrence of spaA and spaB genes in E. tonsillarum has only been documented in one paper, among isolates from ornamental fish (Pomaranski et al, 2017). However, given that the species was defined based only on sequencing of the gyrB gene, it is conceivable that this isolate may have been misclassified.…”

“…However, given that E. rhusiopathiae Clade 1 is more commonly isolated from marine mammals in captivity (Opriessnig et al, 2013;, and Erysipelothrix spp. carrying the spaC gene has recently been associated with disease in fish (Pomaranski et al, 2017), protecting against Erysipelothrix spp. carrying these Spa types could be of greater relevance for aquatic species.…”

Erysipelothrix Spp.: Past, Present, and Future Directions in Vaccine Research

“…In recent years Erysipelothrix spp. isolates containing SpaC have been associated with increased fish mortality (16) in the USA and very recently SpaC has also been identified in Erysipelothrix sp. 2 isolates from turkeys with increased mortality in Brazil (127).…”

“…infection in pigs and is well-known by veterinarians and other occupations connected to the food animal industry (14). Today, erysipelas is also used to describe clinical manifestations associated with this bacterium in other species including mammals, fish, birds and reptiles (15,16). In humans, where the disease was first described in 1870 (17) since 1909 the term "erysipeloid" is used (18).…”

“…infections had minimal impacts on livestock production, erysipelas appears to be re-emerging today due to changing environmental conditions, changes in welfare regulations, an increase in outdoor organic farming (41), and changes in antimicrobial usage, with global reductions and eventual bans anticipated in the very near future (42). Sporadic outbreaks are being reported in various settings such as in farmed animals (31,35,(43)(44)(45)(46) and more specifically organic farms (47,48), in fish (16,49) as well as globally in wild animal species (50,51). Climate change could favor increased bacterial loads and persistent environmental contamination.…”