33
Weissella ceti
Characteristics of the Disease
Weissellosis has been described in rainbow trout, and between 2010 and 2012 was
reported to occur on fi ve farms in Brazil, with disease signs of haemorrhagic septicaemia (Costa et al. 2015 ). In addition, the disease has been reported in China and
the USA, and caused substantive mortalities in market-sized fi sh (Snyder et al.
2015 ).
Isolation
Diseased tissues were inoculated onto Columbia blood agar with incubation at
37 °C for 24 h (Vela et al. 2011 ). Costa et al. ( 2015 ) inoculated brain, eye, kidney
and liver tissue were inoculated onto 5 % (v/v) sheep blood agar and MRS agar with
incubation at 25 °C for 48 h
Characteristics of the Pathogen
Box 2.6: Weissella ceti
Cultures on blood agar are 0.75–1.0 mm in diameter, nonpigmented and α
-haemolytic. The cultures contain Gram-positive facultatively anaerobic,
nonmotile asporogenous coccoid rods occurring singly or in pairs. Growth
occurs at 22–37 °C, but not at 15 or 42 °C, and in 3–6.5 % (w/v) sodium
chloride, and not at pH 3.9. Alkaline and acid phosphatases, naphthol-AS-BIphosphohydrolase and pyrazinamidase, but not N-acetyl-ß-glucosaminidase,
catalase, α-chymotrypsin, cysteine arylamidase, esterase (C4), ester lipase
(C8), α-fucosidase, α- or ß-galactosidase, α- or ß-glucosidase, ß- glucuronidase,
lipase (C14), leucine arylamidase, α- or ß-mannosidase, trypsin or valine arylamidase is produced. Acid is produced from N-acetylglucosamine, D-glucose,
maltose, D ribose trehalose, but not from D-adonitol, aesculin, amygdalin,
L- or D-arabinose, L- or D-arabitol, arbutin, cellobioise, dulcitol, erythritol,
D-fructose, D-galactose, gentiobiose, glycerol, glycogen, inositol, inulin, lactose, D-mannitol, D-mannose, melezitose, melibiose, methyl α-Dglucopyranoside, 2- or 5-ketogluconate, raffi nose, L-rhamnose, salicin,
D-sorbitol, starch, sucrose or L- or D-xylose. Nitrates are not reduced. The
Voges Proskauer reaction is positive. Aesculin is degraded, but not gelatin,
sodium hippurate or urea. The G + C ratio of the DNA is 39.2 mol% (Vela
et al. 2011 ). Thirty-four isolates from Brazil were studied genotypically, and
determined to be homogeneous by REP-PCR, enterobacterial repetitive intergenic consensus sequences PCR and pulsed fi eld gel electrophoresis.
Sequencing of the 16S rRNA gene revealed 99 % homology with Weissella
ceti in the GenBank data base (Costa et al. 2015 ).
Leuconostocacceae Representative
Weissella ceti
Characteristics of the Disease
Weissellosis has been described in rainbow trout, and between 2010 and 2012 was
reported to occur on fi ve farms in Brazil, with disease signs of haemorrhagic septicaemia (Costa et al. 2015 ). In addition, the disease has been reported in China and
the USA, and caused substantive mortalities in market-sized fi sh (Snyder et al.
2015 ).
Isolation
Diseased tissues were inoculated onto Columbia blood agar with incubation at
37 °C for 24 h (Vela et al. 2011 ). Costa et al. ( 2015 ) inoculated brain, eye, kidney
and liver tissue were inoculated onto 5 % (v/v) sheep blood agar and MRS agar with
incubation at 25 °C for 48 h
Characteristics of the Pathogen
Box 2.6: Weissella ceti
Cultures on blood agar are 0.75–1.0 mm in diameter, nonpigmented and α
-haemolytic. The cultures contain Gram-positive facultatively anaerobic,
nonmotile asporogenous coccoid rods occurring singly or in pairs. Growth
occurs at 22–37 °C, but not at 15 or 42 °C, and in 3–6.5 % (w/v) sodium
chloride, and not at pH 3.9. Alkaline and acid phosphatases, naphthol-AS-BIphosphohydrolase and pyrazinamidase, but not N-acetyl-ß-glucosaminidase,
catalase, α-chymotrypsin, cysteine arylamidase, esterase (C4), ester lipase
(C8), α-fucosidase, α- or ß-galactosidase, α- or ß-glucosidase, ß- glucuronidase,
lipase (C14), leucine arylamidase, α- or ß-mannosidase, trypsin or valine arylamidase is produced. Acid is produced from N-acetylglucosamine, D-glucose,
maltose, D ribose trehalose, but not from D-adonitol, aesculin, amygdalin,
L- or D-arabinose, L- or D-arabitol, arbutin, cellobioise, dulcitol, erythritol,
D-fructose, D-galactose, gentiobiose, glycerol, glycogen, inositol, inulin, lactose, D-mannitol, D-mannose, melezitose, melibiose, methyl α-Dglucopyranoside, 2- or 5-ketogluconate, raffi nose, L-rhamnose, salicin,
D-sorbitol, starch, sucrose or L- or D-xylose. Nitrates are not reduced. The
Voges Proskauer reaction is positive. Aesculin is degraded, but not gelatin,
sodium hippurate or urea. The G + C ratio of the DNA is 39.2 mol% (Vela
et al. 2011 ). Thirty-four isolates from Brazil were studied genotypically, and
determined to be homogeneous by REP-PCR, enterobacterial repetitive intergenic consensus sequences PCR and pulsed fi eld gel electrophoresis.
Sequencing of the 16S rRNA gene revealed 99 % homology with Weissella
ceti in the GenBank data base (Costa et al. 2015 ).
Leuconostocacceae Representative