67
genetically, serologically and phenotypically homogeneous (Romalde et al. 2008 ;
Valdés et al. 2009 ).
Diagnosis
Molecular Techniques Detection/diagnosis of Str. phocae has quickly been the
subject of molecular-based approaches, with detection levels of 10
2 and 10
4 cells/
per PCR tube achieved for primer pair PX1-PXVQ2 (Avendaño-Herrera 2008 ).
Using seeded Atlantic salmon tissues, this primer pair enabled the detection of
5.1 × 10
5 – 6.4 × 10
7 CFU/g of kidney, liver and spleen, with nested-PCR being most
sensitive (Avendaño-Herrera 2008 ). A multiplex PCR was developed for the simultaneous detection Aer. salmonicida, Pis. salmonis, Str. phocae and V. anguillarum .
The detection limit using purifi ed total bacterial DNA was 5 pg/μl (=1.26 × 10
4 CFU/
ml). The limits of detection using spiked tissues, i.e. kidney, liver, muscle or spleen,
were, 9.03 ± 1.84 × 10
5 CFU/g (Tapia-Cammas et al. 2011 ).
Pathogenicity
Injection of Atlantic salmon with Str. phocae cells but not ECPs led to mortalities
with cultures resisting the killing ability of mucus and serum and multiplying within
them (González-Contreras et al. 2011 ). The latter may be the result of capsular
material. Haemagglutination was not reported. The pathogen was capable of adhering to but not of entering cells [this was determined by use of the CHSE cell line]
(González-Contreras et al. 2011 ). Iron uptake mechanisms involved siderophores
and constitutive iron binding components. At least two iron-regulated membrane
proteins increased when the pathogen was cultured in iron-restricted medium
(Retamales et al. 2012 ).
Box 2.18: Streptococcus phocae
Cultures comprise ß-haemolytic facultatively anaerobic, non-motile, cocci in
pairs or chains, that do not produce catalase. Growth occurs at 37 °C but not
at 10 or 45 °C, or in 6.5 % (w/v) sodium chloride or in 40 % (v/v) bile. Alkaline
phosphatase is produced, but not ß-glucuronidase, hyaluronidase or pyrrolidonyl arylamidase. The Voges Proskauer reaction is negative. Neither aesculin,
hippurate nor starch is degraded. Acid is produced from D-fructose, maltose,
D-mannose, N -acetyl-glucosamine and ribose, but not from galactose, glycerol, inulin, lactose, mannitol, melezitose, D-raffi nose, salicin, sorbitol, or
trehalose. The G + C ratio of the DNA is 38.6 mol% (Skaar et al. 1994 ).
Streptococcaceae Representatives
genetically, serologically and phenotypically homogeneous (Romalde et al. 2008 ;
Valdés et al. 2009 ).
Diagnosis
Molecular Techniques Detection/diagnosis of Str. phocae has quickly been the
subject of molecular-based approaches, with detection levels of 10
2 and 10
4 cells/
per PCR tube achieved for primer pair PX1-PXVQ2 (Avendaño-Herrera 2008 ).
Using seeded Atlantic salmon tissues, this primer pair enabled the detection of
5.1 × 10
5 – 6.4 × 10
7 CFU/g of kidney, liver and spleen, with nested-PCR being most
sensitive (Avendaño-Herrera 2008 ). A multiplex PCR was developed for the simultaneous detection Aer. salmonicida, Pis. salmonis, Str. phocae and V. anguillarum .
The detection limit using purifi ed total bacterial DNA was 5 pg/μl (=1.26 × 10
4 CFU/
ml). The limits of detection using spiked tissues, i.e. kidney, liver, muscle or spleen,
were, 9.03 ± 1.84 × 10
5 CFU/g (Tapia-Cammas et al. 2011 ).
Pathogenicity
Injection of Atlantic salmon with Str. phocae cells but not ECPs led to mortalities
with cultures resisting the killing ability of mucus and serum and multiplying within
them (González-Contreras et al. 2011 ). The latter may be the result of capsular
material. Haemagglutination was not reported. The pathogen was capable of adhering to but not of entering cells [this was determined by use of the CHSE cell line]
(González-Contreras et al. 2011 ). Iron uptake mechanisms involved siderophores
and constitutive iron binding components. At least two iron-regulated membrane
proteins increased when the pathogen was cultured in iron-restricted medium
(Retamales et al. 2012 ).
Box 2.18: Streptococcus phocae
Cultures comprise ß-haemolytic facultatively anaerobic, non-motile, cocci in
pairs or chains, that do not produce catalase. Growth occurs at 37 °C but not
at 10 or 45 °C, or in 6.5 % (w/v) sodium chloride or in 40 % (v/v) bile. Alkaline
phosphatase is produced, but not ß-glucuronidase, hyaluronidase or pyrrolidonyl arylamidase. The Voges Proskauer reaction is negative. Neither aesculin,
hippurate nor starch is degraded. Acid is produced from D-fructose, maltose,
D-mannose, N -acetyl-glucosamine and ribose, but not from galactose, glycerol, inulin, lactose, mannitol, melezitose, D-raffi nose, salicin, sorbitol, or
trehalose. The G + C ratio of the DNA is 38.6 mol% (Skaar et al. 1994 ).
Streptococcaceae Representatives