Should antibiotics be used in combination in sick fish?

[Brockp]

On the ****** koi forum web site I found a list of antibiotics and doses. In the post was a comment “These two can be used at full strength together, to give a broad spectrum”. Which sort of implied that the two following antibiotics in the article could be used together to increase efficacy. Which is incorrect as two antibiotcs that followed were both aminoglycosides and there would be no advantage in using them together, but it got me thinking.

I wondered what other people felt about this so to clarify a few misconceptions and to open the subject up I wrote the following piece. I have tried to keep away from the long words and chemistry as much as possible !

Antibiotics are rarely if ever given on their own when serious are being treated in man, and animal veterinary practice. The routine, particularly if the actual bacteria causing the problem are not known, which is normally the case with our koi, or where we are treating mixed infections with several bugs involved, is to use two or more antibiotics in combination.

There are three main reasons for this;

1) Using one or two or even three antibiotics in combination substantially widens the spectrum of bugs that will be inhibited or killed thus making it more likely that the infection will be controlled.

2) The second reason is even more interesting. This concerns an interesting biological phenomenon known as synergy.
If we assume that antibiotic A has 1 unit of bug killing activity and that antibiotic B also has 1 unit of bug killing activity when they are used separately they would both produce 1 unit of bug killing activity. If however we give them in combination then 1 + 1 does not equal 2 but a much larger number as high as 4 or 6 units of bug killing activity. This multiplier effect when certain antibiotics are given together is synergy. This means that they are much more effective at killing bugs as well as killing a wider spectrum of bugs than when they are given on their own.

3) The last reason for considering combination antibiotics as to reduce the emergence of resistant bacteria which is a major problem for vets, doctors and anybody treating infections. This may come about if the bugs are exposed to sub lethal doses of antibiotics e,g, as inevitably happens when antibiotics are added to pond water or added to food. It also happens when antibiotics are given by injection as some bugs may have found a way to stop an antibiotic being effective e.g. some bugs can break down penicillin and its derivatives by producing an enzyme called penicillinase. If the penicillin is given with another antibiotic that has a different mechanism for killing bugs by hitting some other part of its metabolism then the few bugs that have learnt to make the penicillin destroying enzyme will be killed and we have less chance of accidentally making more bugs resistant to routine antibiotics.

Antibiotic combinations which show synergy are numerous and include combinations of aminoglycosides (Gentamycin*, Amikacin*) with penicillins (Ampicillin, Amoxyl* etc); aminoglycosides with cephalosporins. Note however that there is a theoretical risk that some antibiotic combinations e.g. tetracyclines and penicillins would have an antagonistic effect i.e. 1 + 1 =<2 and should be avoided.

Hope this helps or at least informs so that we ask the right questions when the vet comes to visit.

Peter

[Brockp]

I get the feeling that the vet police are vetting us. I have had to use amikacin plus ampicillin in two fish now with excellent results. The problem is you have give the amp twice or three times a day but the amikacin is once a day. IP route is my prefered route as you cab give the volume without any concerns of local sterile muscle abscesses.
Hey come on somebody argue with me or I may start thinking I am right which would keep me wake nights.
Peter

[Graham.]

Peter I cant argue but I am riveted to seat reading and looking to understand more.

Maybe you, Dunc or Syd can give a little more insight into Antibiotics and a better overview insight as to if certain do better than others for different things.

I know after chatting to Paula last week on a bacterial problem I was facing is that once I went through a variety of things she straight away said this was an Aeromonas bacteria, rather than a Pseudomonas bacteria.

Having an insight for me into this field would give me so much more confidence when understanding what is required, if the situation raised it's head again.

I think in general most of my experience has come from a hands on situation or guidance from friends that have been down that road or of course from support of KQ members, so any nitty gritty insght and a better understanding is always welcome.

Regards

[Gazza]

Hi Peter,

Yes you are correct in what you are saying and i know that sometimes treating with two AB's have had great success in the past and stopped problems in there tracks so a very good way of sometimes getting on top of something nasty.

I think the main problem comes when we are not sure on what we have and have to tack a stab at which AB to use and as we know bacteria can start to build up an immune system against some of out treatments and i do believe that sometimes people do go in for the "jab em up" policy a bit to early for my liking what are your thoughts on this subject

[TicToc]

A really good read Peter, I thoroughly enjoyed the piece. Can't think of any immediate arguements though sadly.

Pip,pip,
Tickers

[Brockp]

Hi Guys;

I have been thinking about writing something on how to choose the right antibiotic. In animals and man one can make a very good educated guess at what the bug is by the appearance of the surrounding tissue, how the bug is spreading and the overall state of the animal; bit more difficult with koi but let me do some research and see if I an come up with a treatment flow diagram for the choice of antibiotics a bit like the excellent floe diagram in Duncan's book.

Then you can all tell me why I get it wrong

Peter

[TicToc]

Morning Peter,

I imagine thats a fair bit of work but like all the others, look forward to seeing the finished chart.

Regards,
TicToc

[Graham.]

Peter good morning, has there been any developement on this?

Many thanks
Graham

[Brockp]

Hi Graham;

I have done a fair bit of research but the literature and actual research is very thin and often relates to fish (mainly rainbow trout and salmon) and is often from the commercial fish farm environment which is very different from our koi ponds....... I am stil as Duncan would say, ploughing through the books and references but for the next few weeks my time is limited due to pressure of work.

Peter

[Graham.]

Hey Peter thanks for getting back. I'll keep popping back to this thread in time.

Thank you.