342
On iron-defi cient medium, many Edw. tarda cultures, notably those associated
with virulence, produced siderophores (Kokubo et al. 1990 ; Mathew et al. 2001 ;
Igarishi et al. 2002 ) and OMPs of which one was considered to be the receptor for
the siderophore under iron-limited conditions. Such components permit the
pathogen to scavenge for iron in the blood of the host. Certainly, it appears that the
ability of Edw. tarda to acquire iron is an important part of the infection process
(Park 1986 ; Iida and Wakabayashi 1990 ), and it is relevant that an iron-regulated
haemolysin gene has been reported (Hirono et al. 1997a ). The virulent strains are
more resistant to the bacteriostasis of iron-chelating reagents than their avirulent
counterparts. There is an indication that exposure to copper attenuate virulence (Hu
et al. 2010 ).
A 70 kb plasmid, which codes antibiotic resistance has been linked to pathogenicity insofar as curing of the plasmid led to attenuation of virulence in goldfi sh and
zebra fi sh models (Yu et al. 2012 ).
Typical of many bacterial pathogens, Edw. tarda adheres to host cells before
internalization, which involves microfi laments and protein tyrosine kinase (Ling
et al. 2000 ). Using green fl uorescent protein (GFP) tagged cells, the portals of entry
after immersion challenge were identifi ed as the digestive tract, i.e. anterior intestine, gills and body surface of blue gourami (Ling et al. 2000 ). The bacteria located
in these sites plus blood, heart, kidney, liver, muscle, posterior intestine and spleen
after 3 days, but declined substantially by 7 days, with only substantial populations
remaining in the intestine. Bacterial OMPS, of which 8 have been recognised as
interacting with 12 fi sh gills proteins, have been described (Liu et al. 2012 ). The
evpP gene, which encodes the T6SS secretory protein, EvpP, has been described as
essential for invasion of host cells (Zhang et al. 2014 ).
Disease Control
Disease Resistant Fish The differential resistance of rohu families has been discussed (Mohanty et al. 2012 ).
Vaccine Development Prophylaxis by vaccination has been successful (e.g.
Gutierrez and Miyazaki 1994 ; Kwon et al. 2006 , 2007 ; Sun et al. 2010a ; Takano
et al. 2011 ), with oral administration of immunostimulants, namely ß-glucan,
levamisole and vitamins C an E heightening protection further, especially if harmful
(afl atoxin B 1 was identifi ed) conditions prevailed (Sahoo and Mukherjee 2002 ).
Eels responded to the administration of heat- or formalin-killed cells (preferably by
injection) by producing humoral antibodies with titres of up to 1:4096 (Song and
Kou 1981 ). Song et al. ( 1982 ) vaccinated eels by immersion for periods of 20 s to
3 min in suspensions containing 10
5 to 10
8 bacterial cells/ml. A trivalent formalininactivated vaccine comprising Edw. tarda, Str. iniae and Str. parauberis, protected
olive fl ounder when administered intraperitoneally in 0.1 ml amounts (Han et al.
2011 ). Furthermore, Takano et al. ( 2011 ) described the success of using
6 Enterobacteriaceae Representatives
On iron-defi cient medium, many Edw. tarda cultures, notably those associated
with virulence, produced siderophores (Kokubo et al. 1990 ; Mathew et al. 2001 ;
Igarishi et al. 2002 ) and OMPs of which one was considered to be the receptor for
the siderophore under iron-limited conditions. Such components permit the
pathogen to scavenge for iron in the blood of the host. Certainly, it appears that the
ability of Edw. tarda to acquire iron is an important part of the infection process
(Park 1986 ; Iida and Wakabayashi 1990 ), and it is relevant that an iron-regulated
haemolysin gene has been reported (Hirono et al. 1997a ). The virulent strains are
more resistant to the bacteriostasis of iron-chelating reagents than their avirulent
counterparts. There is an indication that exposure to copper attenuate virulence (Hu
et al. 2010 ).
A 70 kb plasmid, which codes antibiotic resistance has been linked to pathogenicity insofar as curing of the plasmid led to attenuation of virulence in goldfi sh and
zebra fi sh models (Yu et al. 2012 ).
Typical of many bacterial pathogens, Edw. tarda adheres to host cells before
internalization, which involves microfi laments and protein tyrosine kinase (Ling
et al. 2000 ). Using green fl uorescent protein (GFP) tagged cells, the portals of entry
after immersion challenge were identifi ed as the digestive tract, i.e. anterior intestine, gills and body surface of blue gourami (Ling et al. 2000 ). The bacteria located
in these sites plus blood, heart, kidney, liver, muscle, posterior intestine and spleen
after 3 days, but declined substantially by 7 days, with only substantial populations
remaining in the intestine. Bacterial OMPS, of which 8 have been recognised as
interacting with 12 fi sh gills proteins, have been described (Liu et al. 2012 ). The
evpP gene, which encodes the T6SS secretory protein, EvpP, has been described as
essential for invasion of host cells (Zhang et al. 2014 ).
Disease Control
Disease Resistant Fish The differential resistance of rohu families has been discussed (Mohanty et al. 2012 ).
Vaccine Development Prophylaxis by vaccination has been successful (e.g.
Gutierrez and Miyazaki 1994 ; Kwon et al. 2006 , 2007 ; Sun et al. 2010a ; Takano
et al. 2011 ), with oral administration of immunostimulants, namely ß-glucan,
levamisole and vitamins C an E heightening protection further, especially if harmful
(afl atoxin B 1 was identifi ed) conditions prevailed (Sahoo and Mukherjee 2002 ).
Eels responded to the administration of heat- or formalin-killed cells (preferably by
injection) by producing humoral antibodies with titres of up to 1:4096 (Song and
Kou 1981 ). Song et al. ( 1982 ) vaccinated eels by immersion for periods of 20 s to
3 min in suspensions containing 10
5 to 10
8 bacterial cells/ml. A trivalent formalininactivated vaccine comprising Edw. tarda, Str. iniae and Str. parauberis, protected
olive fl ounder when administered intraperitoneally in 0.1 ml amounts (Han et al.
2011 ). Furthermore, Takano et al. ( 2011 ) described the success of using
6 Enterobacteriaceae Representatives