197
Overall, there was good agreement with the description of Aer. sobria (MartinCarnahan and Joseph 2005 ). In particular, the important differentiating traits
included production of acid from glucose (with gas), mannitol and sucrose but not
salicin, and the inability to degrade aesculin (Martin-Carnahan and Joseph 2005 ).
The only difference to the species description centred on the production of H 2 S. The
isolate recovered by Xu et al. (2014) were tentatively identifi ed by phenotypic traits
and sequencing of the 16S rRNA gene.
Epizootiology
It may be assumed that the natural reservoir is eutrophic fresh water.
Pathogenicity
Cultures were pathogenic to rainbow trout and tilapia with the LD 50 reported as
2 × 10
5 cells and 4.17 × 10
3 CFU, respectively (Li and Cai 2011 ). Dead rainbow trout
revealed the presence of haemorrhagic septicaemia. In addition, thermolabile ECP
were cytotoxic and lethal (30 μg protein/fi sh) to rainbow trout. Paniagua et al.
( 1990 ) highlighted the role of caseinase, haemolysins and cytotoxins in the pathogenic process. Wahli et al. ( 2006 ) noted haemolytic activity on sheep and trout
erythrocytes, and cytotoxicity to EPC cell line.
Isolates identifi ed as Aer. sobria biovar sobria have been found to be pathogenic
to rainbow trout (Orozova et al. 2009 ).
Box 4.8: Aer. sobria
Cultures comprise motile (single polar fl agellum) fermentative Gram-negative
rods, which produce arginine dihydrolase, catalase, ß-galactosidase, indole,
lysine decarboxylase and oxidase, but not H 2 S or ornithine decarboxylase.
Blood, casein, gelatin, starch and Tween 80 are degraded, but not so aesculin,
elastin or urea. Acid is produced from glucose (with gas), mannitol and
sucrose, but not from arabinose, inositol, rhamnose, salicin or sorbitol.
Nitrates are reduced, and the Voges Proskauer reaction is positive. Growth
occurs in 0-5 % but not 10 % (w/v) sodium chloride and on TCBS. Resistance
has been recorded to ampicillin, novobiocin and the vibriostatic agent, O/129.
The G + C ratio of the DNA is 60.4 moles % (Toranzo et al. 1989 ).
Aeromonas sobria
Overall, there was good agreement with the description of Aer. sobria (MartinCarnahan and Joseph 2005 ). In particular, the important differentiating traits
included production of acid from glucose (with gas), mannitol and sucrose but not
salicin, and the inability to degrade aesculin (Martin-Carnahan and Joseph 2005 ).
The only difference to the species description centred on the production of H 2 S. The
isolate recovered by Xu et al. (2014) were tentatively identifi ed by phenotypic traits
and sequencing of the 16S rRNA gene.
Epizootiology
It may be assumed that the natural reservoir is eutrophic fresh water.
Pathogenicity
Cultures were pathogenic to rainbow trout and tilapia with the LD 50 reported as
2 × 10
5 cells and 4.17 × 10
3 CFU, respectively (Li and Cai 2011 ). Dead rainbow trout
revealed the presence of haemorrhagic septicaemia. In addition, thermolabile ECP
were cytotoxic and lethal (30 μg protein/fi sh) to rainbow trout. Paniagua et al.
( 1990 ) highlighted the role of caseinase, haemolysins and cytotoxins in the pathogenic process. Wahli et al. ( 2006 ) noted haemolytic activity on sheep and trout
erythrocytes, and cytotoxicity to EPC cell line.
Isolates identifi ed as Aer. sobria biovar sobria have been found to be pathogenic
to rainbow trout (Orozova et al. 2009 ).
Box 4.8: Aer. sobria
Cultures comprise motile (single polar fl agellum) fermentative Gram-negative
rods, which produce arginine dihydrolase, catalase, ß-galactosidase, indole,
lysine decarboxylase and oxidase, but not H 2 S or ornithine decarboxylase.
Blood, casein, gelatin, starch and Tween 80 are degraded, but not so aesculin,
elastin or urea. Acid is produced from glucose (with gas), mannitol and
sucrose, but not from arabinose, inositol, rhamnose, salicin or sorbitol.
Nitrates are reduced, and the Voges Proskauer reaction is positive. Growth
occurs in 0-5 % but not 10 % (w/v) sodium chloride and on TCBS. Resistance
has been recorded to ampicillin, novobiocin and the vibriostatic agent, O/129.
The G + C ratio of the DNA is 60.4 moles % (Toranzo et al. 1989 ).
Aeromonas sobria