350
Isolation
Cultures were obtained from the internal organs and subcutaneous tissues at the
base of the pelvic fi ns on BHIA and nutrient agar supplemented with 10 % (v/v)
sheep blood following incubation at an unspecifi ed temperature for 48 h, whereupon small, round, smooth colonies developed. Teshima et al. ( 1992 ) isolated the
organism on heart infusion agar following incubation at 30 °C for 2 days.
Characteristics of the Pathogen
In 1988, an apparently new Brucella – like bacterium was described as a pathogen of rainbow trout in Bulgaria (Gelev and Gelev 1988 ). Although antigenic relationships to Brucella abortus were reported, the organism displayed marked
similarities to the Enterobacteriaceae. Subsequent investigation led to a realisation
that the organism was, in fact, Hafnia alvei (Gelev et al. 1990 ). Subsequently, Haf.
alvei was recognised as the cause of mortalities among cherry salmon ( O. masou ) in
Japanese farms (Teshima et al. 1992 ). Isolates matched the species description, with
the exception of lack of motility and utilisation of D-tartrate. As a word of caution,
Haf. alvei may be confused with Y. ruckeri especially if reliance is based on some
phenotypic diagnostic procedures.
It was deemed that there was a common antigenic determinant in the LPS with
Brucella abortus and Y. ruckeri (Gelev and Gelev 1988 ). However, the presence of
motility and the negative reaction in the oxidase test precludes a relationship with
bona fi de Brucella taxa. There was 82–100 % re-association between the fi sh isolates and Haf. alvei (Gelev et al. 1990 ).
Box 6.7: Hafnia alvei
The isolate comprises small coccoid or slightly elongated motile Gramnegative rods which produce catalase, ß-galactosidase and lysine and ornithine decarboxylase, but not arginine dihydrolase, H 2 S, indole or oxidase. The
methyl red, nitrate reduction and citrate utilisation tests and Voges Proskauer
reaction (weakly positive) are positive, but not malonate utilisation or phenylalanine deaminase. Neither aesculin, DNA, gelatin, lipids nor urea is degraded.
Acid is produced from arabinose, cellobiose, glucose (but not gas), glycerol,
maltose, mannose, mannitol, rhamnose, trehalose and xylose, but not from
adonitol, dulcitol, erythritol, lactose, melibiose, raffi nose, salicin, sorbitol or
sucrose. Growth occurs at 41 °C.
6 Enterobacteriaceae Representatives
Isolation
Cultures were obtained from the internal organs and subcutaneous tissues at the
base of the pelvic fi ns on BHIA and nutrient agar supplemented with 10 % (v/v)
sheep blood following incubation at an unspecifi ed temperature for 48 h, whereupon small, round, smooth colonies developed. Teshima et al. ( 1992 ) isolated the
organism on heart infusion agar following incubation at 30 °C for 2 days.
Characteristics of the Pathogen
In 1988, an apparently new Brucella – like bacterium was described as a pathogen of rainbow trout in Bulgaria (Gelev and Gelev 1988 ). Although antigenic relationships to Brucella abortus were reported, the organism displayed marked
similarities to the Enterobacteriaceae. Subsequent investigation led to a realisation
that the organism was, in fact, Hafnia alvei (Gelev et al. 1990 ). Subsequently, Haf.
alvei was recognised as the cause of mortalities among cherry salmon ( O. masou ) in
Japanese farms (Teshima et al. 1992 ). Isolates matched the species description, with
the exception of lack of motility and utilisation of D-tartrate. As a word of caution,
Haf. alvei may be confused with Y. ruckeri especially if reliance is based on some
phenotypic diagnostic procedures.
It was deemed that there was a common antigenic determinant in the LPS with
Brucella abortus and Y. ruckeri (Gelev and Gelev 1988 ). However, the presence of
motility and the negative reaction in the oxidase test precludes a relationship with
bona fi de Brucella taxa. There was 82–100 % re-association between the fi sh isolates and Haf. alvei (Gelev et al. 1990 ).
Box 6.7: Hafnia alvei
The isolate comprises small coccoid or slightly elongated motile Gramnegative rods which produce catalase, ß-galactosidase and lysine and ornithine decarboxylase, but not arginine dihydrolase, H 2 S, indole or oxidase. The
methyl red, nitrate reduction and citrate utilisation tests and Voges Proskauer
reaction (weakly positive) are positive, but not malonate utilisation or phenylalanine deaminase. Neither aesculin, DNA, gelatin, lipids nor urea is degraded.
Acid is produced from arabinose, cellobiose, glucose (but not gas), glycerol,
maltose, mannose, mannitol, rhamnose, trehalose and xylose, but not from
adonitol, dulcitol, erythritol, lactose, melibiose, raffi nose, salicin, sorbitol or
sucrose. Growth occurs at 41 °C.
6 Enterobacteriaceae Representatives