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Antibiotics usage

Neil Frank wrote a few days ago (sorry for the delay, but I did not
have
the chance to log onto my E-mail over the week-end):

<<<I once used Kanamycin when I could't find erythromycin. This is
another 'mycin' sold in aquarium shops. It worked fine. I think
others have also used it on 'resistant strains of blue green algae
(another name for cynaobacteria). Regarding your use of
erythromycin, you might want to wait a few more days before you give
up on its effectiveness. I have found that its and other algicide's
effects are not noticed immediately. You did not say how many daily
treatments of erythromycin you used.  The label for fish disease
recommends 1 200mg capsule per 10 gallon(40 liters), for several
days. This corresponds to 5.0 mg/l per day. As you also did, I
usually try 1/2 dose or 2.5 mg/l.>>>


Neil and Olive, please note the following:

1) The best way to create antibiotic-resistant bacterial strains is
to use low doses multiple times. Full doses for at least 5-7 days
(this is a very, very general rule with many exceptions) should be
used to minimize this problem, considering that  even a full-dose,
full-lenght antibiotic treatment may induce onset of resistance. As
far as I know, the labels of many antibiotics for aquarium use err
on the underdosing side for liability reasons, and to use even less
than what recommended would make things worse.

2) Antimicrobial resistance is in most cases extended to all
antibiotics of a given class, and sometimes to antibiotics of
different classes. In other words, creating resistance to one
antibiotic may not be always overcome using a different one.

3) As you pointed out, all the sensitive microbial flora in the tank
(and in the fish) is going to be affected. In particular, in
addition to cyanobacteria other beneficial bacteria (in the filter,
on the fish mucosas, etc.) are killed as well (sometimes more
efficiently than the bad ones!). 

4) Human infections due to selection of antibiotic resistant strains
in animals is a reality for food animals. I do not know if use of
antibiotics in aquaria can or will ever be linked to human
epidemics, but a word of general caution is needed here. Low levels
of antibiotics may persist in the aquatic environment (in the tank
sediment, in the sewer system) with prolonged effects on the
microbial flora (which most consider minor, but some do not).


Risks and benefits, as always, should be carefully balanced. 
To some extent this is an individual choice.  In this
case my feeling is that antibiotics should be used (carefully) to
treat diseases. They do nothing on the environmental conditions that
make some bacteria thrive, and actually they may worsen these
conditions inhibiting the metabolism of some nutrients. This list
has provided me with tons of advice of how to get rid of blue-green
algae (with no antibiotics), and it worked!



Dionigi 



dionigi.maladorno at roche_com

All opinions expressed are strictly personal