32
Isolation
Swabbed material of ascites, brain, kidney and liver were inoculated onto sheep
blood agar with incubation at 25 °C for 72 h (Figueiredo et al. 2012 ).
Characteristics of the Pathogen
Seventy seven isolates were obtained and equated with Weissella by phenotyping
and by sequencing of the 16S rRNA gene. The US isolates were 99 % homologous
with those from China and Brazil (Welch and Good 2013 ).
Epizootiology
Figueiredo et al. ( 2012 ) considered that transmission occurred through water.
Pathogenicity
Isolates infected fi sh in laboratory-based challenge experiments of rainbow trout
involving use of i.m. and i.p. injection and immersion (Figueiredo et al. 2012 ).
Control
Vaccine Formalised whole cells were protective when administered by injection;
the RPS was reported 87.5 % and 85 % at 38 and 72 days after vaccination, respectively (Welch and Good 2013 ). Moreover, the preparation could be combined successfully as a bivalent product with ERM antigens (Welch and Good 2013 ).
Box 2.5: Weissella sp.
Colonies contain Gram-positive cocci, that do not produce catalase or oxidase, and are variable for α-haemolysis. Growth occurs over a wide range of
temperatures (20–45 °C), but not on MacConkey agar. Acid is produced from
D-maltose, pullulan, D-ribose and D-trehalose, but not from D-arabitol,
α-cyclodextrin, glycogen, D-lactose, D-mannitol, D-melibiose, D-melezitose,
D-saccharose, D-sorbitol or D-tagatose. The Voges Proskauer reaction is positive. Aesculin and sodium hippurate (variable result) are attacked. L-arginine
is hydrolysed by some isolates. Pyruvate, 2-naphthyl-ß-D-galactopyranoside,
L-leucyl-2-naphthylamide, naphthol α-D-glucuronate, 2-naphthylphosphate
and pyrrolidonyl-2-naphthylamide were not metabolised. There is a >98 %
16S rRNA sequence homology with Weissella (Figueiredo et al. 2012 ).
2 Gram-Positive Bacteria (Anaerobes and ‘Lactic Acid’ Bacteria)
Isolation
Swabbed material of ascites, brain, kidney and liver were inoculated onto sheep
blood agar with incubation at 25 °C for 72 h (Figueiredo et al. 2012 ).
Characteristics of the Pathogen
Seventy seven isolates were obtained and equated with Weissella by phenotyping
and by sequencing of the 16S rRNA gene. The US isolates were 99 % homologous
with those from China and Brazil (Welch and Good 2013 ).
Epizootiology
Figueiredo et al. ( 2012 ) considered that transmission occurred through water.
Pathogenicity
Isolates infected fi sh in laboratory-based challenge experiments of rainbow trout
involving use of i.m. and i.p. injection and immersion (Figueiredo et al. 2012 ).
Control
Vaccine Formalised whole cells were protective when administered by injection;
the RPS was reported 87.5 % and 85 % at 38 and 72 days after vaccination, respectively (Welch and Good 2013 ). Moreover, the preparation could be combined successfully as a bivalent product with ERM antigens (Welch and Good 2013 ).
Box 2.5: Weissella sp.
Colonies contain Gram-positive cocci, that do not produce catalase or oxidase, and are variable for α-haemolysis. Growth occurs over a wide range of
temperatures (20–45 °C), but not on MacConkey agar. Acid is produced from
D-maltose, pullulan, D-ribose and D-trehalose, but not from D-arabitol,
α-cyclodextrin, glycogen, D-lactose, D-mannitol, D-melibiose, D-melezitose,
D-saccharose, D-sorbitol or D-tagatose. The Voges Proskauer reaction is positive. Aesculin and sodium hippurate (variable result) are attacked. L-arginine
is hydrolysed by some isolates. Pyruvate, 2-naphthyl-ß-D-galactopyranoside,
L-leucyl-2-naphthylamide, naphthol α-D-glucuronate, 2-naphthylphosphate
and pyrrolidonyl-2-naphthylamide were not metabolised. There is a >98 %
16S rRNA sequence homology with Weissella (Figueiredo et al. 2012 ).
2 Gram-Positive Bacteria (Anaerobes and ‘Lactic Acid’ Bacteria)