102
RTG-2 cells with some escape into the cytoplasm (González et al. 1999 ). Within the
phagocytic cells, renibacterium exhibits a slow rate of division, and survives certainly for 10 or more days (Gutenberger et al. 1997 ). Conversely, the macrophages
may well inhibit the growth of and kill renibacterium by the live bacterial cells
generating respiratory burst products (Hardie et al. 1996 ; Campos-Pérez et al.
1997 ). With this scenario, exposure to Ren. salmoninarum would enhance the killing activity of the macrophages (Hardie et al. 1996 ).
The hydrophobic, soluble cell surface p57 protein is common to all isolates (Wiens
and Dale 2009 ), and is released in large quantities as a monomer into the external
environment from broth cultures and in infected fi sh (Wiens et al. 1999 ). It is responsible for cell agglutination e.g. of salmonid leucocytes (Senson and Stevenson 1999 ;
Wiens et al. 1999 ), and is encoded by msa [= major soluble antigen] genes – msa1
and msa2 and msa3 [this is a duplicate of msa1 but is not present in all isolates of
Ren. salmoninarum; Rhodes et al. 2002 , 2004a ], both msa1 and msa2 are needed for
complete virulence (Coady et al. 2006 ). It is produced in comparatively large amounts
and consequently has been a target for vaccine development. The role of p57 protein
in the pathogenicity process has prompted some excellent research. Incubation of
Ren. salmoninarum at 37 °C for >4 h decreased cell surface hydrophobicity (this
decrease was negated by pre-incubation in PMSF), as measured by salt aggregation,
and decreased the quantity of cell-associated p57 protein (Piganelli et al. 1999 ). Cell
surface hydrophobicity was re-instigated following incubation in ECP; refl ecting reassociation of the p57 protein onto the bacterial cell surface (Piganelli et al. 1999 ).
An attenuated culture, MT 239, differs from virulent isolates in expressing less p57
protein (O’Farrell and Strom 1999 ). It has been demonstrated that a Norwegian isolate, strain 684, lacked a specifi c epitope [designated 4C11] and contained single
alanine to glutamine substitution in the amino terminal region resulted in enhanced
binding to leucocytes from Chinook salmon (Wiens et al. 2002 ).
There is a divergent opinion as to the presence of biological activity in ECP of
Ren. salmoninarum . One view is that the ECP is generally devoid of extracellular
enzymes; haemolytic and cytolytic activity being absent (Bandín et al. 1991 ). Yet in
other investigations, proteases (Sakai et al. 1989b ) and haemolysins (Grayson et al.
1995a , 2001 ) have been detected. ECP at 0.1 mg/ml and 1.0 ml/ml inhibited respiratory burst but not phagocytic activity in brook trout splenic phagocytes (Densmore
et al. 1998 ). Hydrophobicity, haemagglutination and haemolysin activity to rabbit
and trout erythrocytes have been recorded from water soluble extracts (proteins)
(Bandin et al. 1989; Daly and Stevenson 1987 ; 1990 ; Evenden et al. 1990 ). In particular, hydrophobicity and auto-aggregation have been linked with virulence
(Bruno 1988 ). Ren. salmoninarum has agglutinated spermatozoa from salmonids
and goldfi sh (Daly and Stevenson 1989 ). Shieh ( 1989 b) reported an unidentifi ed
toxin from Renibacterium, which was lethal to fi ngerling Atlantic salmon. Also, an
iron acquisition mechanism has been found (Grayson et al. 1995b ).
There is some evidence that fi sh respond to infection with renibacterium by the
production of stress factors, including plasma cortisol and lactate, and reduced levels of plasma glucose (Mesa et al. 1999 ). Thus, a 70 kDa stress protein (HSP70) was
recognised in coho salmon with BKD (Forsyth et al. 1997 ).
3 Aerobic Gram-Positive Rods and Cocci
RTG-2 cells with some escape into the cytoplasm (González et al. 1999 ). Within the
phagocytic cells, renibacterium exhibits a slow rate of division, and survives certainly for 10 or more days (Gutenberger et al. 1997 ). Conversely, the macrophages
may well inhibit the growth of and kill renibacterium by the live bacterial cells
generating respiratory burst products (Hardie et al. 1996 ; Campos-Pérez et al.
1997 ). With this scenario, exposure to Ren. salmoninarum would enhance the killing activity of the macrophages (Hardie et al. 1996 ).
The hydrophobic, soluble cell surface p57 protein is common to all isolates (Wiens
and Dale 2009 ), and is released in large quantities as a monomer into the external
environment from broth cultures and in infected fi sh (Wiens et al. 1999 ). It is responsible for cell agglutination e.g. of salmonid leucocytes (Senson and Stevenson 1999 ;
Wiens et al. 1999 ), and is encoded by msa [= major soluble antigen] genes – msa1
and msa2 and msa3 [this is a duplicate of msa1 but is not present in all isolates of
Ren. salmoninarum; Rhodes et al. 2002 , 2004a ], both msa1 and msa2 are needed for
complete virulence (Coady et al. 2006 ). It is produced in comparatively large amounts
and consequently has been a target for vaccine development. The role of p57 protein
in the pathogenicity process has prompted some excellent research. Incubation of
Ren. salmoninarum at 37 °C for >4 h decreased cell surface hydrophobicity (this
decrease was negated by pre-incubation in PMSF), as measured by salt aggregation,
and decreased the quantity of cell-associated p57 protein (Piganelli et al. 1999 ). Cell
surface hydrophobicity was re-instigated following incubation in ECP; refl ecting reassociation of the p57 protein onto the bacterial cell surface (Piganelli et al. 1999 ).
An attenuated culture, MT 239, differs from virulent isolates in expressing less p57
protein (O’Farrell and Strom 1999 ). It has been demonstrated that a Norwegian isolate, strain 684, lacked a specifi c epitope [designated 4C11] and contained single
alanine to glutamine substitution in the amino terminal region resulted in enhanced
binding to leucocytes from Chinook salmon (Wiens et al. 2002 ).
There is a divergent opinion as to the presence of biological activity in ECP of
Ren. salmoninarum . One view is that the ECP is generally devoid of extracellular
enzymes; haemolytic and cytolytic activity being absent (Bandín et al. 1991 ). Yet in
other investigations, proteases (Sakai et al. 1989b ) and haemolysins (Grayson et al.
1995a , 2001 ) have been detected. ECP at 0.1 mg/ml and 1.0 ml/ml inhibited respiratory burst but not phagocytic activity in brook trout splenic phagocytes (Densmore
et al. 1998 ). Hydrophobicity, haemagglutination and haemolysin activity to rabbit
and trout erythrocytes have been recorded from water soluble extracts (proteins)
(Bandin et al. 1989; Daly and Stevenson 1987 ; 1990 ; Evenden et al. 1990 ). In particular, hydrophobicity and auto-aggregation have been linked with virulence
(Bruno 1988 ). Ren. salmoninarum has agglutinated spermatozoa from salmonids
and goldfi sh (Daly and Stevenson 1989 ). Shieh ( 1989 b) reported an unidentifi ed
toxin from Renibacterium, which was lethal to fi ngerling Atlantic salmon. Also, an
iron acquisition mechanism has been found (Grayson et al. 1995b ).
There is some evidence that fi sh respond to infection with renibacterium by the
production of stress factors, including plasma cortisol and lactate, and reduced levels of plasma glucose (Mesa et al. 1999 ). Thus, a 70 kDa stress protein (HSP70) was
recognised in coho salmon with BKD (Forsyth et al. 1997 ).
3 Aerobic Gram-Positive Rods and Cocci