57
opacity and haemorrhaging in the eye, and surface and internal (mostly in the spleen
and fat around the intestine) haemorrhaging leading to death (Lahav et al. 2004 ).
Isolation
Heart infusion agar supplemented with thallium acetate and oxolinic acid or with
colistin sulphate and oxolinic acid was evaluated for the selective recovery of Str.
iniae from Japanese fl ounder and the fi sh farm environment. Defi brinated horse
blood was also added to determine haemolysin pattern. The result was recovery of
Str. iniae from brain, intestine and kidney of diseased fi sh (Nguyen and Kanai 1999 ).
Characteristics of the Pathogen
On the basis of DNA:DNA hybridisation, i.e. 77–100 % DNA homology, Str.
iniae was realised to be synonymous with Str. shiloi, which had been previously
named as the causal agent of a septicaemic condition in cultured fi sh, which occurred
in Israel in 1984 (Eldar et al. 1994 , 1995a , b ). This change in the taxonomy was
confi rmed by others (e.g. Tiexeira et al. 1996 ). The organism was recovered from
rainbow trout, which had been previously vaccinated with a streptococcus vaccine,
with the conclusion that a new serotype had emerged (Bachrach et al. 2001 ). Indeed,
a study of 26 Israeli and 9 other isolates using phenotypic, RAPD, and AFLP and
16S rDNA sequencing revealed a new variant among the Israeli cultures (Kvitt and
Box 2.15: Streptococcus iniae (= Str. shiloi)
Colonies on BHIA are 1 mm in diameter, and non-pigmented after incubation
aerobically for 24 h at 30 °C. Cultures comprise fermentative, catalase and
oxidase-negative [virulent cultures are encapsulated; Barnes et al. 2003a ]
Gram-positive cocci in pairs and chains (some degree of pleomorphism has
been observed), which grow at 37 °C but not at 10 or 45 °C, or in 40 % bile or
6.5 % (w/v) sodium chloride, but do grow at pH 9.6. Isolates attack (produced
acid from) N-acetyl-glucosamine, aesculin, arbutin, cellobiose, D-fructose,
gentiobiose, D-glucose, glycogen, maltose, mannitol, D-mannose, melezitose, ribose, salicin, starch and trehalose, but not adonitol, amygdalin, L- or
D-arabinose, L- or D-arabitol, dulcitol, erythritol, L- or D-fucose, galactose,
gluconate, glycerol, inositol, inulin, lactose, melibiose, D-raffi nose, rhamnose, sorbitol, L-sorbose, tagatose, turanose, xylitol, or L- or D-xylose.
Alkaline phosphatase, arginine dihydrolase, ß-glucuronidase, leucine arylamidase and pyrrolidonylarylamidase are produced, but not α- or
ß- galactosidase. The Voges Proskauer reaction is negative. Nitrates are not
reduced. α-haemolysis is recorded for bovine blood. Aesculin but not gelatin
or sodium hippurate is degraded (Eldar et al. 1994 ; Zhou et al. 2008 ).
Streptococcaceae Representatives
opacity and haemorrhaging in the eye, and surface and internal (mostly in the spleen
and fat around the intestine) haemorrhaging leading to death (Lahav et al. 2004 ).
Isolation
Heart infusion agar supplemented with thallium acetate and oxolinic acid or with
colistin sulphate and oxolinic acid was evaluated for the selective recovery of Str.
iniae from Japanese fl ounder and the fi sh farm environment. Defi brinated horse
blood was also added to determine haemolysin pattern. The result was recovery of
Str. iniae from brain, intestine and kidney of diseased fi sh (Nguyen and Kanai 1999 ).
Characteristics of the Pathogen
On the basis of DNA:DNA hybridisation, i.e. 77–100 % DNA homology, Str.
iniae was realised to be synonymous with Str. shiloi, which had been previously
named as the causal agent of a septicaemic condition in cultured fi sh, which occurred
in Israel in 1984 (Eldar et al. 1994 , 1995a , b ). This change in the taxonomy was
confi rmed by others (e.g. Tiexeira et al. 1996 ). The organism was recovered from
rainbow trout, which had been previously vaccinated with a streptococcus vaccine,
with the conclusion that a new serotype had emerged (Bachrach et al. 2001 ). Indeed,
a study of 26 Israeli and 9 other isolates using phenotypic, RAPD, and AFLP and
16S rDNA sequencing revealed a new variant among the Israeli cultures (Kvitt and
Box 2.15: Streptococcus iniae (= Str. shiloi)
Colonies on BHIA are 1 mm in diameter, and non-pigmented after incubation
aerobically for 24 h at 30 °C. Cultures comprise fermentative, catalase and
oxidase-negative [virulent cultures are encapsulated; Barnes et al. 2003a ]
Gram-positive cocci in pairs and chains (some degree of pleomorphism has
been observed), which grow at 37 °C but not at 10 or 45 °C, or in 40 % bile or
6.5 % (w/v) sodium chloride, but do grow at pH 9.6. Isolates attack (produced
acid from) N-acetyl-glucosamine, aesculin, arbutin, cellobiose, D-fructose,
gentiobiose, D-glucose, glycogen, maltose, mannitol, D-mannose, melezitose, ribose, salicin, starch and trehalose, but not adonitol, amygdalin, L- or
D-arabinose, L- or D-arabitol, dulcitol, erythritol, L- or D-fucose, galactose,
gluconate, glycerol, inositol, inulin, lactose, melibiose, D-raffi nose, rhamnose, sorbitol, L-sorbose, tagatose, turanose, xylitol, or L- or D-xylose.
Alkaline phosphatase, arginine dihydrolase, ß-glucuronidase, leucine arylamidase and pyrrolidonylarylamidase are produced, but not α- or
ß- galactosidase. The Voges Proskauer reaction is negative. Nitrates are not
reduced. α-haemolysis is recorded for bovine blood. Aesculin but not gelatin
or sodium hippurate is degraded (Eldar et al. 1994 ; Zhou et al. 2008 ).
Streptococcaceae Representatives