59
mortalities in terms of statistical signifi cance (Bromage and Owens 2009 ). Also,
co-infection of Str. iniae with aquabirnavirus has led to higher mortalities in
Japanese fl ounder (Pakingking et al. 2003 ).
Polysaccharide capsules have been found on Str. iniae (Barnes et al. 2003a ), with
evidence that the capsule may be involved with the resistance to opsonophagocytosis in yellowtail (Yoshida et al. 1997 ). This view by was reinforced by Miller and
Neely ( 2005 ), who when using capsular mutants showed that the polysaccharide
capsule was indeed important for the virulence of Str. iniae. Again, an effect on
avoiding phagocytosis by avoiding phagocytic clearance was reported (Lowe et al.
2007 ; Locke et al. 2007 ). Eyngor et al. 2008 ) described the emergence of an extracellular polysaccharide producing strain of Str. iniae and thus the (re-)occurrence of
disease outbreaks following vaccination.
A surface-located α-enolase, which is a plasmin and plasminogen binding and
cell wall associating protein and may be associated with tissue invasion, has been
found in Str. iniae . This enzyme may help Str. iniae to cross tissue barriers (Kim
et al. 2007 ). Moreover, there is sound evidence for an extracellular polysaccharide
leading to death of rainbow trout (Eyngor et al. 2010 ).
The pathogen produces a cytolysin with haemolytic traits, which is a functional
homologue of streptolysin S. Expression of this cytolysin is necessary for local tissue necrosis but not to bacteraemia (Fuller et al. 2002 ). When grown in serum, this
streptococcus expresses surface factors that are capable of binding to trout immunoglobulin by the Fc region [= crystallisable fragment of the immunoglobulin] (Barnes
et al. 2003b ). A range of isolates from fi sh, a dolphin and humans produced apoptosis and/or necrosis in tilapia nonspecifi c cytotoxic cells and tilapia continuous cell
line (Taylor et al. 2001 ). Only serotype II strains entered, multiplied and survived in
pronephros phagocytes (leading to apoptosis) for >48 h. This is relevant because it
was estimated that ~70 % of the bacteria contained in blood during sepsis were
located within phagocytes, which suggests a preferred intracellular existence
(Zlotkin et al. 2003 ).
Scavenging for iron is necessary for the survival of pathogens within host tissues.
Siderophores have been found in Str. iniae. Instead, the pathogen has been
determined to require iron-containing proteins for growth under conditions of
iron- restriction. Indeed, the ABC transporter system was recognized to be responsible for haem utilization. A putative lipoprotein exerts a role in haem utilization
and is produced in vivo during infection with the pathogen (Wang et al. 2013 ).
A putative bacteriocin, Sil, which is composed of 101 amino acid residues, is
secreted by Str. iniae, interacted with turbot head kidney monocytes inhibiting the
innate immune response of the host cells and enhancing the cellular infection of the
pathogen. The data suggested that Sil promotes infection by impairing the immune
system of the fi sh (Li et al 2014 ).
Examination by GC-MS of the metabolites important to the defence of tilapia
against infection highlighted the importance of elevated N-acetylglucosamine levels in survivors. Thus, supplying the chemical to fi sh enhanced survival (Cheng
et al. 2014 ).
Streptococcaceae Representatives
mortalities in terms of statistical signifi cance (Bromage and Owens 2009 ). Also,
co-infection of Str. iniae with aquabirnavirus has led to higher mortalities in
Japanese fl ounder (Pakingking et al. 2003 ).
Polysaccharide capsules have been found on Str. iniae (Barnes et al. 2003a ), with
evidence that the capsule may be involved with the resistance to opsonophagocytosis in yellowtail (Yoshida et al. 1997 ). This view by was reinforced by Miller and
Neely ( 2005 ), who when using capsular mutants showed that the polysaccharide
capsule was indeed important for the virulence of Str. iniae. Again, an effect on
avoiding phagocytosis by avoiding phagocytic clearance was reported (Lowe et al.
2007 ; Locke et al. 2007 ). Eyngor et al. 2008 ) described the emergence of an extracellular polysaccharide producing strain of Str. iniae and thus the (re-)occurrence of
disease outbreaks following vaccination.
A surface-located α-enolase, which is a plasmin and plasminogen binding and
cell wall associating protein and may be associated with tissue invasion, has been
found in Str. iniae . This enzyme may help Str. iniae to cross tissue barriers (Kim
et al. 2007 ). Moreover, there is sound evidence for an extracellular polysaccharide
leading to death of rainbow trout (Eyngor et al. 2010 ).
The pathogen produces a cytolysin with haemolytic traits, which is a functional
homologue of streptolysin S. Expression of this cytolysin is necessary for local tissue necrosis but not to bacteraemia (Fuller et al. 2002 ). When grown in serum, this
streptococcus expresses surface factors that are capable of binding to trout immunoglobulin by the Fc region [= crystallisable fragment of the immunoglobulin] (Barnes
et al. 2003b ). A range of isolates from fi sh, a dolphin and humans produced apoptosis and/or necrosis in tilapia nonspecifi c cytotoxic cells and tilapia continuous cell
line (Taylor et al. 2001 ). Only serotype II strains entered, multiplied and survived in
pronephros phagocytes (leading to apoptosis) for >48 h. This is relevant because it
was estimated that ~70 % of the bacteria contained in blood during sepsis were
located within phagocytes, which suggests a preferred intracellular existence
(Zlotkin et al. 2003 ).
Scavenging for iron is necessary for the survival of pathogens within host tissues.
Siderophores have been found in Str. iniae. Instead, the pathogen has been
determined to require iron-containing proteins for growth under conditions of
iron- restriction. Indeed, the ABC transporter system was recognized to be responsible for haem utilization. A putative lipoprotein exerts a role in haem utilization
and is produced in vivo during infection with the pathogen (Wang et al. 2013 ).
A putative bacteriocin, Sil, which is composed of 101 amino acid residues, is
secreted by Str. iniae, interacted with turbot head kidney monocytes inhibiting the
innate immune response of the host cells and enhancing the cellular infection of the
pathogen. The data suggested that Sil promotes infection by impairing the immune
system of the fi sh (Li et al 2014 ).
Examination by GC-MS of the metabolites important to the defence of tilapia
against infection highlighted the importance of elevated N-acetylglucosamine levels in survivors. Thus, supplying the chemical to fi sh enhanced survival (Cheng
et al. 2014 ).
Streptococcaceae Representatives