106
that erythromycin, dosed at 100 mg of drug/kg body weight of fi sh/day for 21 days,
gave the best result. The value of erythromycin at this concentration was confi rmed
by Austin ( 1985 ), although it was suggested that treatment need only be continued
for 10 days. Erythromycin has also been reported to prevent vertical transmission of
renibacteria (Evelyn et al. 1986b ; Brown et al. 1990 ). Also, an injection of 20 mg of
erythromycin/kg of broodstock fi sh is useful in preventing vertical transmission
(Lee and Evelyn 1994 ). However, there is evidence for the development of a reduction in susceptibility to macrolide antibiotics (Rhodes et al. 2008 ).
Aerococcaceae Representative
Aerococcus viridans
Characteristics of the Disease
A disease, which led to losses of 30–40 %, was reported among farmed tilapia in
Southwest China during 2010, with signs including congestion of the gills and
abdomen, swollen gall bladder, and diffuse liver. Some fi sh displayed exophthalmia
and spiral swimming behaviour (Ke et al. 2012 ).
Isolation
Isolation was achieved from brain and liver samples from moribund tilapia, using
BHIA and sheep blood agar with incubation at 28 °C for up to 48 h.
Characteristics of the Pathogen
By use of the Rapid ID 32 Strep system, identifi cation of Aerococcus viridans
was achieved (99 % certainty of a correct identifi cation. This was confi rmed by
Box 3.3: Aerococcus viridans
Off-white colonies are 1–2 mm in diameter after incubation for 48 h at 28 °C,
and contain non-motile, α-haemolytic Gram-positive cocci of 0.6–2.0 μm in
diameter in pairs, tetrads or small clusters. Neither arginine dihydrolase, catalase, ß-N-acetyl-glucosamine, Ala-Phe-Pro-arylamidase, alkaline phosphatase, glycyl tryptophan arylamidase, α-or ß-galactosidase, ß-glucuronidase,
leucine aminopeptidase, pyroglutamic acid arylamidase, oxidase nor urease is
produced. The Voges Prokauer reaction is negative. Growth occurs in 6.5 %
(w/v) NaCl (Ke et al. 2012 ).
3 Aerobic Gram-Positive Rods and Cocci
that erythromycin, dosed at 100 mg of drug/kg body weight of fi sh/day for 21 days,
gave the best result. The value of erythromycin at this concentration was confi rmed
by Austin ( 1985 ), although it was suggested that treatment need only be continued
for 10 days. Erythromycin has also been reported to prevent vertical transmission of
renibacteria (Evelyn et al. 1986b ; Brown et al. 1990 ). Also, an injection of 20 mg of
erythromycin/kg of broodstock fi sh is useful in preventing vertical transmission
(Lee and Evelyn 1994 ). However, there is evidence for the development of a reduction in susceptibility to macrolide antibiotics (Rhodes et al. 2008 ).
Aerococcaceae Representative
Aerococcus viridans
Characteristics of the Disease
A disease, which led to losses of 30–40 %, was reported among farmed tilapia in
Southwest China during 2010, with signs including congestion of the gills and
abdomen, swollen gall bladder, and diffuse liver. Some fi sh displayed exophthalmia
and spiral swimming behaviour (Ke et al. 2012 ).
Isolation
Isolation was achieved from brain and liver samples from moribund tilapia, using
BHIA and sheep blood agar with incubation at 28 °C for up to 48 h.
Characteristics of the Pathogen
By use of the Rapid ID 32 Strep system, identifi cation of Aerococcus viridans
was achieved (99 % certainty of a correct identifi cation. This was confi rmed by
Box 3.3: Aerococcus viridans
Off-white colonies are 1–2 mm in diameter after incubation for 48 h at 28 °C,
and contain non-motile, α-haemolytic Gram-positive cocci of 0.6–2.0 μm in
diameter in pairs, tetrads or small clusters. Neither arginine dihydrolase, catalase, ß-N-acetyl-glucosamine, Ala-Phe-Pro-arylamidase, alkaline phosphatase, glycyl tryptophan arylamidase, α-or ß-galactosidase, ß-glucuronidase,
leucine aminopeptidase, pyroglutamic acid arylamidase, oxidase nor urease is
produced. The Voges Prokauer reaction is negative. Growth occurs in 6.5 %
(w/v) NaCl (Ke et al. 2012 ).
3 Aerobic Gram-Positive Rods and Cocci