548
A disease, resembling vibriosis and equated to a new species V. trachurii, has
been long associated with Japanese horse mackerel (Trachurus japonicus) especially during summer when the seawater temperature exceeds 25 °C (Iwamoto et al.
1995 ). Infected fi sh displayed erratic swimming, darkened in colour, developed pronounced bilateral exophthalmia, and developed haemorrhages on the internal
organs. However, the organism is now recognised as synonym of V. harveyi
(Thompson et al. 2002 ).
The organism has been recovered in mixed communities with V. anguillarum and
V. chagassi from sand melts with skin haemorrhages (Fabbro et al. 2011 ).
There has been a gradual awareness of the increasing signifi cance of V. harveyi
as a killer of marine fi sh and penaeids. Saeed ( 1995 ) blamed V. harveyi with causing
mortalities in cultured brown spotted grouper (Epinephelus tauvina) and silvery
black porgy (Acanthopagrus cuvieri) in Kuwait.
Isolation
Samples of kidney and liver were inoculated into thioglycollate broth (Appendix in
Chap. 12 ), followed by single colony isolation on plates of TSA supplemented with
1 % (w/v) sodium chloride (Grimes et al. 1984a ). Yii et al. ( 1997 ) used TSA supplemented with 2 % (w/v) sodium chloride and TCBS with intestinal fl uid from diseased grouper. Generally, the use of TSA, MacConkey agar, TCBS and cytophaga
agar were advocated, with incubation at 25–35 °C for 24–48 h. Thus according to
Kraxberger-Beatty et al. ( 1990 ), the eyes were removed and homogenised in sterile
saline; loopfuls of the material being streaked onto the agar-containing media.
It should be emphasised that attempts were not made to surface sterilise the eyes.
Therefore, the resulting homogenate would have also contained aquatic (saprophytic) bacteria, as well as any potential pathogen.
Characteristics of the Pathogen
Twelve cultures were recovered from corneas, and were identifi ed as V. harveyi as a
result of biochemical tests and DNA:DNA hybridisation (90–94 % DNA homology
with the type strain of V. harveyi). Certainly, the characteristics of the isolates were
in good accord with the species description of V. harveyi (Farmer et al. 2005 ). A
result of DNA:DNA hybridisation, Ishimaru and Muroga ( 1997 ) determined that
pathogenic vibrios recovered from milkfi sh in Japan were indeed V. harveyi.
The synonymy of V. harveyi and V. carchariae was realised by Pedersen et al.
( 1998 ) as a result of phenotypic and genotypic studies, and by Gauger and GómezChiarri ( 2002 ) from 16S rDNA sequencing. In terms of taxonomic standing, harveyi has precedence, and therefore this name will be used in preference to
carchariae.
10 Vibrios
A disease, resembling vibriosis and equated to a new species V. trachurii, has
been long associated with Japanese horse mackerel (Trachurus japonicus) especially during summer when the seawater temperature exceeds 25 °C (Iwamoto et al.
1995 ). Infected fi sh displayed erratic swimming, darkened in colour, developed pronounced bilateral exophthalmia, and developed haemorrhages on the internal
organs. However, the organism is now recognised as synonym of V. harveyi
(Thompson et al. 2002 ).
The organism has been recovered in mixed communities with V. anguillarum and
V. chagassi from sand melts with skin haemorrhages (Fabbro et al. 2011 ).
There has been a gradual awareness of the increasing signifi cance of V. harveyi
as a killer of marine fi sh and penaeids. Saeed ( 1995 ) blamed V. harveyi with causing
mortalities in cultured brown spotted grouper (Epinephelus tauvina) and silvery
black porgy (Acanthopagrus cuvieri) in Kuwait.
Isolation
Samples of kidney and liver were inoculated into thioglycollate broth (Appendix in
Chap. 12 ), followed by single colony isolation on plates of TSA supplemented with
1 % (w/v) sodium chloride (Grimes et al. 1984a ). Yii et al. ( 1997 ) used TSA supplemented with 2 % (w/v) sodium chloride and TCBS with intestinal fl uid from diseased grouper. Generally, the use of TSA, MacConkey agar, TCBS and cytophaga
agar were advocated, with incubation at 25–35 °C for 24–48 h. Thus according to
Kraxberger-Beatty et al. ( 1990 ), the eyes were removed and homogenised in sterile
saline; loopfuls of the material being streaked onto the agar-containing media.
It should be emphasised that attempts were not made to surface sterilise the eyes.
Therefore, the resulting homogenate would have also contained aquatic (saprophytic) bacteria, as well as any potential pathogen.
Characteristics of the Pathogen
Twelve cultures were recovered from corneas, and were identifi ed as V. harveyi as a
result of biochemical tests and DNA:DNA hybridisation (90–94 % DNA homology
with the type strain of V. harveyi). Certainly, the characteristics of the isolates were
in good accord with the species description of V. harveyi (Farmer et al. 2005 ). A
result of DNA:DNA hybridisation, Ishimaru and Muroga ( 1997 ) determined that
pathogenic vibrios recovered from milkfi sh in Japan were indeed V. harveyi.
The synonymy of V. harveyi and V. carchariae was realised by Pedersen et al.
( 1998 ) as a result of phenotypic and genotypic studies, and by Gauger and GómezChiarri ( 2002 ) from 16S rDNA sequencing. In terms of taxonomic standing, harveyi has precedence, and therefore this name will be used in preference to
carchariae.
10 Vibrios