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In
the past, when my fish became sick, I use the headache-aspirin approach,
treating with what sounded right. It usually wasn't! I got tired of
wasting money on treatments that did not work. I decided to do some
research. Maybe, if I understood what these antibiotics are, and a little
of how they work, I would feel a little better before popping that tablet
of capsule into the tank. So, writing this article is as much for me
as it is for anyone else. Sooner
or later, all of us breeders are confronted by a bacterial infection
in a tank full of our prized guppies. This problem usually presents
itself after some stressful event. The first thing you do is figure
out "why", and then how to get them better before its too
late. In my case, "too late" usually comes first. There
are dozens of antibiotics, antibacterial's and atimicrobials on the
market, the trick being which to use. So, pick one, or better yet two
and begin chemical warfare on you unsuspecting fish. Of course it's
for their own good. But how do you know it will work? Is it the right
antibiotic? What about killing the good guys? You know, the nitrifiers,
the ones that convert ammonia to nitrite and then to nitrate so that
your gups don't live in a toxic sewer. How
do these tablets or capsules work? We've all heard these names before;
tetracycline, erythromycin, and sulfamides. How do they kill bacteria?
How do they know which bacteria to kill? These are some of the questions
that I had. Microbiology
- The study of microscopic creatures, including bacteria. By
technical definition an antibiotic is a chemical produced by a microorganism,
such as a bacterium or fungus, that it then uses to kill another microorganism.
It's their way of waging chemical warfare on the nearest competition. Bacteria
and, especially, fungi provide most of our antibiotics. The bacteria
in the group streptomyces produce more antibiotics than all other groups
combined. And that blue-green mold that grows on your orange, that's
penicillium, the king of all molds from which Alexander Flemming originally,
isolated penicillin back in 1939. So
you get the idea: an antibiotic is a compound naturally produced by
a microorganism to kill another microorganism. Not to be confused with
an antibacterial which is a compound that was designed in some chemist
lab. These are familiar; SULFA DRUGS, FURANS QUINOLINES (like nalidixic
acid), the so-called designer antibacterial's. Now
a little about bacteria. Bacteria are classified as either gram positive
or gram negative. We've all heard these terms, understanding their meaning
is something else. The way I understand these states of "gramness"
is that they refer to the way that the bacteria stain or hold color
by a particular method. When exposed to this method the gram-positive
bacteria will stain violet and the gram-negative bacteria will stain
pink.
The
major difference in bacteria is due to the structure and composition
of their cell walls. The way the cell wall is put together makes a big
difference in the way that the bacteria respond to antibiotics. It is
said that gram positives respond better to antibiotics that effect their
cell wall, and gram negatives respond better to antibiotics that interfere
with their protein synthesis. There are exceptions on both sides. There
have been over two dozen different bacteria reported from infections
in fish. Except for about half a dozen of these, the majority of warm
water pathogens are gram negative. Of these, the most common infection
in fresh water fish is caused by aeromonas, whereas in saltwater, its
Vibrio. Because
of their cell wall composition, neither of these is susceptible to the
action of penicillin or it's semisynthetic derivatives, such as ampicillin.
Penicillin works best against gram positive bacteria. Penicillin has
a narrow spectrum of action and only works well against a few types
of bacteria, most of which don't infect aquarium fish. The
newer semisynthetic ampicillin has a broader spectrum against even some
gram-negative bacteria, but these medications are still not the drugs
of choice for most fish pathogens. Even though they are big sellers,
antibiotics like penicillin and ampicillin are not effective against
areomonas infections. While
I'm on gram positives, I'll touch on erythromycin. This drug is commonly
used in humans to treat gram positive infections in people who are allergic
to penicillin. Erythromycin works by binding with ribosome's, thus interfering
with the metabolic process of protein synthesis in bacteria. In other
words the bacteria cannot produce the components that it needs to live.
Erythromycin has a broader range than penicillin and it may have a very
limited effect against specific gram negative bacteria. Erythromycin
works best when the pH of the water is neutral or slightly alkaline. Another
group of antibiotics commonly used is aminoglycosides, although most
of us don't recognize them by this name. They are more familiar by the
names: Kanamycin, Neomycin, Streptomycin, and Gentamicin. Of these Neomycin
and Kanamycin are the most commonly used. Both of these are soluble
in water at slightly alkaline pH levels and both provide a broad spectrum
of activity against gram negative bacteria. Aminoglycosides
work to produce a bacterial affect by inhibiting protein synthesis in
bacteria. Usually Neomycin is used to treat superficial skin infections
in fresh water fish, while Kanamycin is used to treat the same infections
in saltwater fish. Caution
should be used when treating with these drugs. They should never be
used in combination or in sequential treatment. I will continue to research antibiotics and how they work and write more articles in the future months. I hope this information is useful. Check back for the second part of this article soon. |