Date: 15 Dec 1997
From: Veter Quimica <bjauregu@reuna.cl>
To: MARINE_PATHOL@VS.vims.EDU
QUESTION:
We are a company based in Santiago de Chile, that sells products for health and animal nutrition, including fishes. I am the marine biologist aboard.
We have isolated a strain of Flavobacterium-like bacteria from juvenile turbot that suffer necrosis in the jaw and dorsal fin destruction. Direct gram from uncultured bacteria from the lesions showed a near-purity slender gram-negative bacteria. Mortality was around 30 % with late treatment with amoxicilline.
The colonies were like F. columnare that adheres to agar. We think that the isolate could be Flexibacter maritimus because it grew in sea water, did not grow on saltless media, and was catalase positive, but it also grew in media (agar-cytophaga) supplemented with 2% salt. This late statement does not agree with the description of F. maritimus by Bernardet et al. (1989)(Int. J. Sys. Bacteriol.39:346-354).
Do you have a hint or a hunch for the bacteria that could meet both
requirements, to grow on sea water and 2% NaCl and not to grow on media without salt, being also catalase positive?
We have a clue from the paper by Bernardet; we think it could be Cytophaga lytica or Cytophaga salmonicolor. We do not have reference strains for F. maritimus nor for C. lytica, neither C. salmonicolor, perhaps you could indicate where we could get them.
Tomislav Jakovljevic
Marine Biologist
R&D VETERQUIMICA
CHILE
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COMMENTS 1:
I think your initial deduction that the isolate could be Flexibacter
maritimus is likely to be correct. The presenting signs of disease, slender Gram negative rods, adherence to agar, are characteristics of F. maritimus. I would not be influenced too greatly by absolute sodium ion concentrations. In a study of F. maritimus isolated from Atlantic salmon, we found that 50/50 isolates grew in 50% seawater and 42/50 isolates grew in 25% seawater. All our isolates had an obligate requirement for Na ions and 10% isolates had an obligate requirement for Mg ions; none of the isolates had an obligate requirement for K or Ca ions.
Reference strains of F. maritimus can be obtained from the National
Collection of Industrial and Marine Bacteria in the UK. I would imagine that the American Type Culture Collection has strains as well.
For your interest, we have isolated F. maritimus from greenback flounder, a native marine flat fish, farmed experimentally here in Tasmania, Australia. The presenting signs were similar to your description: erosion around the mouth and on the lateral fins.
Treatment of the disease in Atlantic salmon has been most effective with trimethoprim. F. maritimus is very sensitive to this antibiotic; in
addition trimethoprim is preferentially concentrated in the skin and so fortuitously maximizes the effect of the antibiotic.
Jeremy Carson
Bacteriologist
Fish Health Unit
Dept. Primary Industry & Fisheries
Tasmania, Australia
e-mail: Jeremy.Carson@dpif.tas.gov.au
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