63
Use of Antimicrobial Compounds Success has been reported with the fl uoroquinolone compound, enrofl oxacin, dosed at 5 or 10 mg/kg body weight of fi sh/day for
10 days (Stoffregen et al. 1996 ). Mortalities declined rapidly upon initiating treatment, such that by the end of treatment, a total of 11 % and 17 % of the treated fi sh
has died compared to 55 % and 40 % of the untreated controls, respectively. Also,
laboratory studies have indicated the value of oxytetracycline (Darwish et al. 2003)
and amoxicillin (Darwish and Ismaiel 2003 ) for the control of infection in blue
tilapia and sunshine bass, respectively. Experimental evidence has pointed to the
effi cacy of using amoxicillin for controlling Str. iniae infection especially when
dosed at 80 mg/kg of fi sh/day for 12 days when mortalities dropped from 96 % in
the controls to 6 % in the treated blue tilapia (Darwish and Hobbs 2005 ). Moreover,
the treated survivors did not carry the pathogen
Streptococcus milleri
Characteristics of the Disease
During 1992, Gram-positive chaining cocci and atypical Aer. salmonicida were
recovered from newly imported koi carp, which displayed pronounced surface
ulcers of 4–20 mm in diameter on the fl ank or tail. Internal damage was not recorded
(Austin and Robertson 1993 ).
Characteristics of the Pathogen
Two cultures were obtained from kidney samples in ulcerated koi carp (Austin and
Robertson 1993 ). The following characteristics were displayed:
Box 2.16: Streptococcus milleri
Cultures contain catalase and oxidase-negative fermentative cocci in chains,
that produce acid and alkaline phosphatase, arginine dihydrolase, chemotrypsin, esterase (caprylate and lipase), ß-galactosidase, leucine and valine arylamidase and pyrrolidonylarylamidase but not cystine arylamidase,
α-fucosidase, α -galactosidase, α – and ß-glucosidase, ß-glucuronidase, H 2 S,
indole, α -mannosidase, nitrate reductase, trypsin or tryptophan deaminase.
The methyl red and bile aesculin tests are negative. Aesculin, arginine, casein
and horse blood (weakly ß-haemolytic) are degraded, but not DNA, gelatin,
sodium hippurate, starch or urea. Growth occurs in 0–1.5 % but not 8 % (w/v)
sodium chloride and on MacConkey agar. Citrate is utilised. Acid is produced
from N-acetyl-glucosamine, amygdalin, D-fructose, D-glucose, inositol,
maltose, D-mannose, α-methyl-D-glucoside, ribose, saccharose, sucrose,
D-trehalose, xylitol and xylose, but not from L-arabinose, glycogen, inulin,
lactose, D-mannitol, D-melibiose, raffi nose, rhamnose or sorbitol.
Streptococcaceae Representatives
Use of Antimicrobial Compounds Success has been reported with the fl uoroquinolone compound, enrofl oxacin, dosed at 5 or 10 mg/kg body weight of fi sh/day for
10 days (Stoffregen et al. 1996 ). Mortalities declined rapidly upon initiating treatment, such that by the end of treatment, a total of 11 % and 17 % of the treated fi sh
has died compared to 55 % and 40 % of the untreated controls, respectively. Also,
laboratory studies have indicated the value of oxytetracycline (Darwish et al. 2003)
and amoxicillin (Darwish and Ismaiel 2003 ) for the control of infection in blue
tilapia and sunshine bass, respectively. Experimental evidence has pointed to the
effi cacy of using amoxicillin for controlling Str. iniae infection especially when
dosed at 80 mg/kg of fi sh/day for 12 days when mortalities dropped from 96 % in
the controls to 6 % in the treated blue tilapia (Darwish and Hobbs 2005 ). Moreover,
the treated survivors did not carry the pathogen
Streptococcus milleri
Characteristics of the Disease
During 1992, Gram-positive chaining cocci and atypical Aer. salmonicida were
recovered from newly imported koi carp, which displayed pronounced surface
ulcers of 4–20 mm in diameter on the fl ank or tail. Internal damage was not recorded
(Austin and Robertson 1993 ).
Characteristics of the Pathogen
Two cultures were obtained from kidney samples in ulcerated koi carp (Austin and
Robertson 1993 ). The following characteristics were displayed:
Box 2.16: Streptococcus milleri
Cultures contain catalase and oxidase-negative fermentative cocci in chains,
that produce acid and alkaline phosphatase, arginine dihydrolase, chemotrypsin, esterase (caprylate and lipase), ß-galactosidase, leucine and valine arylamidase and pyrrolidonylarylamidase but not cystine arylamidase,
α-fucosidase, α -galactosidase, α – and ß-glucosidase, ß-glucuronidase, H 2 S,
indole, α -mannosidase, nitrate reductase, trypsin or tryptophan deaminase.
The methyl red and bile aesculin tests are negative. Aesculin, arginine, casein
and horse blood (weakly ß-haemolytic) are degraded, but not DNA, gelatin,
sodium hippurate, starch or urea. Growth occurs in 0–1.5 % but not 8 % (w/v)
sodium chloride and on MacConkey agar. Citrate is utilised. Acid is produced
from N-acetyl-glucosamine, amygdalin, D-fructose, D-glucose, inositol,
maltose, D-mannose, α-methyl-D-glucoside, ribose, saccharose, sucrose,
D-trehalose, xylitol and xylose, but not from L-arabinose, glycogen, inulin,
lactose, D-mannitol, D-melibiose, raffi nose, rhamnose or sorbitol.
Streptococcaceae Representatives