Necrotic myositis of rainbow trout, Oncorhynchus mykiss (Walbaum): proteolytic characteristics of a crude extracellular preparation from Flavobacterium psychrophilum

Abstract

A crude extracellular preparation (CEP) from a strain of Flavobacteriumpsychrophilum recovered from a case of necrotic myositis affecting rainbow trout was capable of causing severe muscle necrosis in rainbow trout following intramuscular injection. Cell wall‐associated preparations, however, were unable to produce similar lesions in experimentally injected fish. The CEP degraded gelatin and type II collagen but not type I or type IV collagen. Furthermore, the CEP did not degrade 2‐furanacryloyl‐ l‐leucylglycyl‐ l‐prolyl‐alanine (FALGPA), chondroitin sulphates A, B or C, heparan sulphate, keratan sulphate, hyaluronic acid, elastin or rainbow trout erythrocytes. The addition of the protease inhibitors 1,10‐phenanthroline, ethylenediamine‐tetraacetic acid (EDTA) and EGTA to the CEP halted its ability to degrade gelatin in vitro and to produce muscle necrosis in rainbow trout in vivo. In vitro and in vivo activity was restored following the addition of 1 m m zinc chloride to the protease inhibitor‐treated CEP, suggesting that this strain of F. psychrophilum secretes a protein complex with zinc metalloprotease‐like activity. This protein complex, therefore, appears to be involved in the pathogenesis of necrotic myositis in rainbow trout.

Complete genome sequence of the fish pathogen Flavobacterium psychrophilum

“…Because many bacterial pathogens produce extracellular collagenolytic enzymes allowing the colonization of connective tissues of their vertebrate hosts, the secretion of extracellular collagenase was considered of importance to F. psychrophilum pathogenicity 16 . Surprisingly, the JIP02/86 genome contains a collagenase-encoding gene that is disrupted by an insertion sequence of the IS256 family.…”

Development of Genetic Techniques for the Psychrotrophic Fish Pathogen Flavobacterium psychrophilum

“…Cells of F. psychrophilum produce a number of proteases that may play a role in the disease process (3). A correlation has been established between the presence of specific proteases and virulence (13,20). The metalloprotease Fpp1, which may be involved in pathogenicity, has recently been purified and characterized (23).…”

High Nutrient Concentration Can Induce Virulence Factor Expression and Cause Higher Virulence in an Environmentally Transmitted Pathogen

“…However, the actual function and role of collagenase in F. columnare virulence have not been studied further. In the closely related fish pathogen, Flavobacterium psychrophilum, collagenase has been connected with virulence [34,38] but opposite results have also been obtained [13,50], and thus, its role in pathogenesis of F. psychrophilum has remained uncertain. Our results could not directly link collagenase with the virulent colony type of F. columnare, and it remains to be studied whether some other processes, such as temporal regulation of virulence factors (similar to e.g.…”