Rifabutin is one of a number of drugs suggested for the treatment of humans
infected with nontuberculous mycobacteria such as "Fishkeepers disease". I
have not been able to find any successful treatment reports of curing fish
with a confirmed mycobacterial infection - not yet anyway?
Here's a little bit of information that might be of interest?
Many nontuberculous mycobacteria are resistant to the drugs commonly used
successfully in the treatment of tuberculosis (e.g., isoniazid,
pyrazinamide, and streptomycin). Antibiotic regimens may require several
(five or six) drugs including rifampin, which is quite effective against M.
kansasii, or clarithromycin, which has marked activity against the M.
avium-intracellulare complex. Surgical resection is occasionally recommended
with or without chemotherapy. In treating disseminated infections in AIDS
patients, a regimen of five or six drugs, including clarithromycin,
ethambutol and perhaps rifabutin, should be considered.
The mutation rates of mycobacteria are very high, meaning that they quickly
adapt to their changing environment. Genetic mutation can develop as often
as once in every million divisions(1,000,000). Each time a genetic mutation
appears, there is a small chance that the mutation will result in immunity
to antibiotic drugs that might otherwise have killed the mycobacterium.
Tubercles (granulomas in the disease tuberculosis) can contain up to one
hundred billion mycobacteria (100,000,000,000), so the chances of the
mycobacteria developing resistance to any individual drug is very high.
If a patient with a mycobacterial infection is treated with only one drug,
the disease may appear to improve temporarily, as most of the bacteria are
destroyed. However, the disease will usually return, when the bacteria with
resistance to that one drug have had a chance to multiply. Remember that
only a very small number of viable mycobacteria are necessary to establish
infection. Use of that one drug in that same patient is then useless, since
the infecting bacteria are resistant to it.
For this reason, mycobacterial infections are almost always treated with a
combination of two or more drugs. The chances of a genetic mutation
resulting in resistance to two or more drugs at the same time are extremely
small.
Since mycobacteria are extremely hardy, drug treatment times are extremely
long. Many species of mycobacteria can become "inactive" for long periods of
time, i.e. they do not metabolise. Antibiotics can only be effective against
a bacterium if that bacterium is metabolising. To completely eradicate a
mycobacterial infection with antibiotics requires that the course be long
enough to act against bacteria that are "hibernating" as well as active
bacteria.
To eradicate a pulmonary(lung) tuberculosis infection takes between six and
nine months of treatment. Tuberculosis outside the lung may take even longer
to treat. If the antibiotic drugs are not taken until the infection is
eradicated (e.g.. the patient stops taking the drugs after two months,
because s/he is feeling better), this gives the bacteria a chance to develop
resistance to the drugs and it is likely that the patient will relapse with
the disease. In this case, the drugs used can not be used again, since the
infecting bacteria will be resistant to them.
Adrian.
Adrian R. Tappin
Brisbane, Australia.
"Home of the Rainbowfish"
http://www.ecn.net.au/~atappin/home.htm