108
Characteristics of the Pathogens
From these data, a link with Bacillus was made. However, there is insuffi cient
information to achieve a proper identifi cation.
A second report appertained to bacillary necrosis among catfi sh in Vietnam. The
bacteria were described as comprising 1 mm diameter, cream coloured colonies on
TSA after 24 h incubation at 28 °C. The cells were Gram-variable, long thin motile,
oxidase-positive rods, that were unreactive towards sugars, and grew at
15–37 °C. H 2 S was produced, and gelatin was attacked. Curiously, there was not
any mention about the presence of endospores. However, by 16S rRNA sequencing,
the nearest match at 95 % homology was Bacillus fumarioli (Ferguson et al. 2001 ).
Pathogenicity
Oladosu et al. 1994 ) infected Clarias gariepinus via the oral and subcutaneous
routes with a comparatively low dose of 0.5 ml, which contained 1.8 × 10
3 cells/ml.
Thus, 60 % and 30 % mortalities were achieved over a three-week period by oral and
subcutaneous challenge, respectively.
Ferguson et al. ( 2001 ) reported that 2 × 10
7 cells of the putative Bacillus injected
intraperitoneally led to clinical disease.
Disease Control
Use of Antimicrobial Compounds It was reported that Bacillus sp. was sensitive
to tetracycline but not penicillin (Oladosu et al. ( 1994 ).
Bacillus cereus
There has been occasional mention of B. cereus as a fi sh pathogen causing
branchionecrosis in common carp (Pychynski et al. 1981 ) and striped bass
(Baya et al. 1992a , b ). However, the supporting evidence is weak.
Box 3.4: Bacillus sp.
Using nutrient agar plates with an incubation temperature of 37 °C, cream,
rough opaque colonies may be obtained. These colonies comprise non motile,
fermentative Gram-positive rods of 1–4 μm in length, which contain central
and oval endospores. The cells grow at 45 °C but not 50 °C, and are not
haemolytic.
3 Aerobic Gram-Positive Rods and Cocci
Characteristics of the Pathogens
From these data, a link with Bacillus was made. However, there is insuffi cient
information to achieve a proper identifi cation.
A second report appertained to bacillary necrosis among catfi sh in Vietnam. The
bacteria were described as comprising 1 mm diameter, cream coloured colonies on
TSA after 24 h incubation at 28 °C. The cells were Gram-variable, long thin motile,
oxidase-positive rods, that were unreactive towards sugars, and grew at
15–37 °C. H 2 S was produced, and gelatin was attacked. Curiously, there was not
any mention about the presence of endospores. However, by 16S rRNA sequencing,
the nearest match at 95 % homology was Bacillus fumarioli (Ferguson et al. 2001 ).
Pathogenicity
Oladosu et al. 1994 ) infected Clarias gariepinus via the oral and subcutaneous
routes with a comparatively low dose of 0.5 ml, which contained 1.8 × 10
3 cells/ml.
Thus, 60 % and 30 % mortalities were achieved over a three-week period by oral and
subcutaneous challenge, respectively.
Ferguson et al. ( 2001 ) reported that 2 × 10
7 cells of the putative Bacillus injected
intraperitoneally led to clinical disease.
Disease Control
Use of Antimicrobial Compounds It was reported that Bacillus sp. was sensitive
to tetracycline but not penicillin (Oladosu et al. ( 1994 ).
Bacillus cereus
There has been occasional mention of B. cereus as a fi sh pathogen causing
branchionecrosis in common carp (Pychynski et al. 1981 ) and striped bass
(Baya et al. 1992a , b ). However, the supporting evidence is weak.
Box 3.4: Bacillus sp.
Using nutrient agar plates with an incubation temperature of 37 °C, cream,
rough opaque colonies may be obtained. These colonies comprise non motile,
fermentative Gram-positive rods of 1–4 μm in length, which contain central
and oval endospores. The cells grow at 45 °C but not 50 °C, and are not
haemolytic.
3 Aerobic Gram-Positive Rods and Cocci