360
kidney sections indicated the presence of Gram-negative bacteria which exhibited
bipolar staining. In a separate development during 1990, the organism was attributed to low level mortalities in turbot, farmed in fl oating cages in France. With this
outbreak, the disease signs included swelling and liquefaction of the kidney and
spleen, which were also characterised by the presence of yellowish nodules
(Vigneulle and Baudin-Laurencin 1995 ). In 1999, Arctic charr in the USA were also
found to be infected with the pathogen (Starliper 2001 ). The external signs centred
on a slight redness and swelling around the anus, but internally there was evidence
of severe hemorrhaging with bloody ascites
Isolation
Isolation was readily achieved from kidney by inoculation of swabbed material
onto BHIA and TSA with incubation at 25 °C for 24–48 h (McIntosh and Austin
1990b ).
Characteristics of the Pathogen
These organisms were recovered as dense pure culture growth from diseased tissues, and were examined bacteriologically (McIntosh and Austin 1990b ).
Box 6.14: Serratia liquefaciens
Cultures comprise Gram-negative fermentative catalase positive rods of
2–3 μm in length which, in contrast to the normal characteristics of the
Enterobacteriaceae (Grimont and Grimont 2005b ), are motile by single polar
fl agella. Intracellular bipolar staining properties are exhibited. Catalase,
ß-galactosidase and lysine and ornithine decarboxylase are produced, but not
H 2 S, indole or tryptophan deaminase. The results of the oxidase test are variable, i.e. from negative to weakly positive depending to some extent on the
age of the culture. The methyl red test and Voges Proskauer reaction is negative. Nitrates are not reduced. Blood (ß-haemolysis), casein, DNA, lecithin
(weak), tributyrin (slow), Tween 20, 40, 60 and 80, and tyrosine are degraded,
but not chitin, elastin, starch or urea. Growth occurs at 4–37 °C, in 0–5 %
(w/v) but not 7 % (w/v) sodium chloride, and on deoxycholate citrate agar,
eosin methylene blue agar and MacConkey agar, but not in 40 % (v/v) bile
salts. Sodium citrate but not sodium malonate is utilised. Acid is produced
from amygdalin, arabinose, inositol, mannose, melibiose and saccharose, but
not rhamnose. Acid and gas are produced from fructose, galactose, glucose,
maltose, mannitol, melibiose, raffi nose, sorbitol, sucrose, trehalose and
xylose. The G + C ratio of the DNA is 55 moles % (McIntosh and Austin
1990b ).
6 Enterobacteriaceae Representatives
kidney sections indicated the presence of Gram-negative bacteria which exhibited
bipolar staining. In a separate development during 1990, the organism was attributed to low level mortalities in turbot, farmed in fl oating cages in France. With this
outbreak, the disease signs included swelling and liquefaction of the kidney and
spleen, which were also characterised by the presence of yellowish nodules
(Vigneulle and Baudin-Laurencin 1995 ). In 1999, Arctic charr in the USA were also
found to be infected with the pathogen (Starliper 2001 ). The external signs centred
on a slight redness and swelling around the anus, but internally there was evidence
of severe hemorrhaging with bloody ascites
Isolation
Isolation was readily achieved from kidney by inoculation of swabbed material
onto BHIA and TSA with incubation at 25 °C for 24–48 h (McIntosh and Austin
1990b ).
Characteristics of the Pathogen
These organisms were recovered as dense pure culture growth from diseased tissues, and were examined bacteriologically (McIntosh and Austin 1990b ).
Box 6.14: Serratia liquefaciens
Cultures comprise Gram-negative fermentative catalase positive rods of
2–3 μm in length which, in contrast to the normal characteristics of the
Enterobacteriaceae (Grimont and Grimont 2005b ), are motile by single polar
fl agella. Intracellular bipolar staining properties are exhibited. Catalase,
ß-galactosidase and lysine and ornithine decarboxylase are produced, but not
H 2 S, indole or tryptophan deaminase. The results of the oxidase test are variable, i.e. from negative to weakly positive depending to some extent on the
age of the culture. The methyl red test and Voges Proskauer reaction is negative. Nitrates are not reduced. Blood (ß-haemolysis), casein, DNA, lecithin
(weak), tributyrin (slow), Tween 20, 40, 60 and 80, and tyrosine are degraded,
but not chitin, elastin, starch or urea. Growth occurs at 4–37 °C, in 0–5 %
(w/v) but not 7 % (w/v) sodium chloride, and on deoxycholate citrate agar,
eosin methylene blue agar and MacConkey agar, but not in 40 % (v/v) bile
salts. Sodium citrate but not sodium malonate is utilised. Acid is produced
from amygdalin, arabinose, inositol, mannose, melibiose and saccharose, but
not rhamnose. Acid and gas are produced from fructose, galactose, glucose,
maltose, mannitol, melibiose, raffi nose, sorbitol, sucrose, trehalose and
xylose. The G + C ratio of the DNA is 55 moles % (McIntosh and Austin
1990b ).
6 Enterobacteriaceae Representatives