354
Plesiomonas shigelloides
Characteristics of the Disease
Although there have been unauthenticated verbal reports that Plesiomonas shigelloides may be pathogenic to fi sh, it was not until the summer of 1984 that the organism was defi nitely recovered from diseased rainbow trout in northern Portugal (Cruz
et al. 1986 ). Subsequently, the organism was recovered in Germany from catfi sh,
which had originated in Nigeria, sturgeon fi ngerlings, which had been sent from
Russia, gourami imported from Thailand and eels (Klein et al. 1993 ). Symptoms
included emaciation, reddening of the anus with yellow exudation, petechial haemorrhages in the internal muscle wall, and sometimes the accumulation of ascitic
fl uid in the peritoneal cavity (Cruz et al. 1986 ). Inappetance was noted by Klein
et al. ( 1993 ). More recently, the organism was isolated from diseased cichlids in
India (Nisha et al. 2014 ).
Isolation
This was accomplished by inoculating samples of kidney and liver onto plates of
TSA with incubation at 22–37 °C for an unspecifi ed period whereupon round,
raised, off-white, circular colonies developed (Cruz et al. 1986 ).
Characteristics of the Pathogen
Many of the characteristics of the pathogen were derived from use of the API 20E
rapid identifi cation system (Cruz et al. 1986 ) and API 20NE system (Klein et al.
1993 ).
Box 6.10: Plesiomonas shigelloides
Colonies contain motile, fermentative Gram-negative rods, which produce
arginine dihydrolase, catalase, ß-galactosidase, indole, lysine and ornithine
decarboxylase and oxidase, but not H 2 S, phenylalanine deaminase, tryptophan deaminase or urease. Nitrates are reduced to nitrite, but negative reactions are recorded for gelatin liquefaction, the methyl red test, utilisation of
citrate or malonate, and the Voges Proskauer reaction. Acid is produced from
glucose, inositol and trehalose, but not from adonitol, aesculin, amygdalin,
L-arabinose, dulcitol, lactose, mannitol, melibiose, raffi nose, rhamnose, salicin, sorbitol, sucrose or xylose. Growth occurs at 22 and 37 °C but not at 4 °C,
and in 0 % (w/v) sodium chloride (Cruz et al. 1986 ; Klein et al. 1993 ).
6 Enterobacteriaceae Representatives
Plesiomonas shigelloides
Characteristics of the Disease
Although there have been unauthenticated verbal reports that Plesiomonas shigelloides may be pathogenic to fi sh, it was not until the summer of 1984 that the organism was defi nitely recovered from diseased rainbow trout in northern Portugal (Cruz
et al. 1986 ). Subsequently, the organism was recovered in Germany from catfi sh,
which had originated in Nigeria, sturgeon fi ngerlings, which had been sent from
Russia, gourami imported from Thailand and eels (Klein et al. 1993 ). Symptoms
included emaciation, reddening of the anus with yellow exudation, petechial haemorrhages in the internal muscle wall, and sometimes the accumulation of ascitic
fl uid in the peritoneal cavity (Cruz et al. 1986 ). Inappetance was noted by Klein
et al. ( 1993 ). More recently, the organism was isolated from diseased cichlids in
India (Nisha et al. 2014 ).
Isolation
This was accomplished by inoculating samples of kidney and liver onto plates of
TSA with incubation at 22–37 °C for an unspecifi ed period whereupon round,
raised, off-white, circular colonies developed (Cruz et al. 1986 ).
Characteristics of the Pathogen
Many of the characteristics of the pathogen were derived from use of the API 20E
rapid identifi cation system (Cruz et al. 1986 ) and API 20NE system (Klein et al.
1993 ).
Box 6.10: Plesiomonas shigelloides
Colonies contain motile, fermentative Gram-negative rods, which produce
arginine dihydrolase, catalase, ß-galactosidase, indole, lysine and ornithine
decarboxylase and oxidase, but not H 2 S, phenylalanine deaminase, tryptophan deaminase or urease. Nitrates are reduced to nitrite, but negative reactions are recorded for gelatin liquefaction, the methyl red test, utilisation of
citrate or malonate, and the Voges Proskauer reaction. Acid is produced from
glucose, inositol and trehalose, but not from adonitol, aesculin, amygdalin,
L-arabinose, dulcitol, lactose, mannitol, melibiose, raffi nose, rhamnose, salicin, sorbitol, sucrose or xylose. Growth occurs at 22 and 37 °C but not at 4 °C,
and in 0 % (w/v) sodium chloride (Cruz et al. 1986 ; Klein et al. 1993 ).
6 Enterobacteriaceae Representatives