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Author Topic: Can antibiotics affect sharks?  (Read 4964 times)

Offline Eric A. Taylor

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Can antibiotics affect sharks?
« on: 05/04/2011 08:43:49 »
I just started listening to Naked Oceans and in the very first podcast I found a story that bothers me quite a lot.

The story involved microbes discovered in sharks that are very resistant to antibiotics. The assumption was that this is a result of the human use of antibiotics, but I find it very hard to imagine how sharks from all over the planet could be coming into contact with human made antibiotics in concentrations high enough to effect their internal microbes. Isn't it much more likely (and interesting if) this is natural? Perhaps something in the shark's immune system is responsible. After all look what sharks do for a living. They attack and eat other fish or animals who usually have no wish to be eaten. They fight back and chances are they do some damage to the shark.

Not once was the possibility of a natural antibiotic property of these fascinating fish mentioned (I happen to love sharks). To be honest I'm getting a little sick of the homo-centric attitude of many of the sciences programs available. They'd have you believe that every single problem on Earth is caused by humans. It's not science, it's anti-science. It's a return to pre-Copernican thinking.
« Last Edit: 02/05/2011 21:49:31 by chris »


 

Offline CliffordK

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Re: Can antibiotics affect sharks?
« Reply #1 on: 05/04/2011 19:46:25 »
I would think it would depend a lot on the antibiotic. 

For example, a natural antibiotic such as Penicillin is found in molds, and the kinds of things that a scavenger might eat, so it might not be surprising to find Penicillin resistant flora in the sharks.

However, for other types of antibiotic resistance, one would have to come up with a plausible mechanism for it to enter the shark's food chain.

For example.  If a fish farm fed salmon smolt antibiotics, then the salmon might develop antibiotic resistant bacteria.  Then, if these smolt were released into the ocean, sharks might eat the fish and be colonized by antibiotic resistant salmon bacteria.  Through the wonders of plasmids and gene transference, some shark flora might also pick up the resistance genes even though there might be little selective pressure to maintain these genes.

Another mechanism might be the release of untreated human sewage into rivers, streams, and the ocean carrying antibiotic resistant bacteria which could then colonize fish, and eventually colonize sharks. 

It should be possible to determine if the specific bacteria carrying the resistance began as human flora.

Many types of antibiotics are not found in the natural environment, and thus it would be unlikely that resistance to these antibiotics would develop without human involvement.

The reality is that this poses little danger to the sharks themselves, but could eventually lead back to us in that standard antibiotics could loose effectiveness.  Most of the multi-drug resistant bacteria are limited to the hospital setting, but eventually might increase in prevalence outside of the hospital setting.  The use of things such as antibacterial soaps should be limited only to those few situations where they are required.
« Last Edit: 05/04/2011 19:51:02 by CliffordK »
 

Offline Bored chemist

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Re: Can antibiotics affect sharks?
« Reply #2 on: 05/04/2011 19:58:52 »
"Many types of antibiotics are not found in the natural environment, and thus it would be unlikely that resistance to these antibiotics would develop without human involvement."

Sure about that?




From wiki "The term "antibiotic" was coined by Selman Waksman in 1942 to describe any substance produced by a microorganism that is antagonistic to the growth of other microorganisms in high dilution.[3] This definition excluded substances that kill bacteria but are not produced by microorganisms (such as gastric juices and hydrogen peroxide). It also excluded synthetic antibacterial compounds such as the sulfonamides. Many antibacterial compounds are relatively small molecules with a molecular weight of less than 2000 atomic mass units.
With advances in medicinal chemistry, most of today's antibacterials chemically are semisynthetic modifications of various natural compounds"

I accept that there's a good chance that we are responsible for antibiotic resistant bugs in many environments, but we can't be the only reason.
 

Offline Eric A. Taylor

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Re: Can antibiotics affect sharks?
« Reply #3 on: 06/04/2011 00:50:46 »
I would think it would depend a lot on the antibiotic. 

For example, a natural antibiotic such as Penicillin is found in molds, and the kinds of things that a scavenger might eat, so it might not be surprising to find Penicillin resistant flora in the sharks.

However, for other types of antibiotic resistance, one would have to come up with a plausible mechanism for it to enter the shark's food chain.

For example.  If a fish farm fed salmon smolt antibiotics, then the salmon might develop antibiotic resistant bacteria.  Then, if these smolt were released into the ocean, sharks might eat the fish and be colonized by antibiotic resistant salmon bacteria.  Through the wonders of plasmids and gene transference, some shark flora might also pick up the resistance genes even though there might be little selective pressure to maintain these genes.

Another mechanism might be the release of untreated human sewage into rivers, streams, and the ocean carrying antibiotic resistant bacteria which could then colonize fish, and eventually colonize sharks. 

It should be possible to determine if the specific bacteria carrying the resistance began as human flora.

Many types of antibiotics are not found in the natural environment, and thus it would be unlikely that resistance to these antibiotics would develop without human involvement.

The reality is that this poses little danger to the sharks themselves, but could eventually lead back to us in that standard antibiotics could loose effectiveness.  Most of the multi-drug resistant bacteria are limited to the hospital setting, but eventually might increase in prevalence outside of the hospital setting.  The use of things such as antibacterial soaps should be limited only to those few situations where they are required.

I would think that fish farmers would only very rarely dump there fish into the ocean. The number of fish in the ocean that came from fish farms is very very small.

Is far as sewage dumps, I suppose it's possible but again it will very quickly be diluted A LOT, so unless the shark is spending quite a lot of time hanging out by the outflow of these dump sites they won't be exposed to very high concentrations. Considering that sharks have "the entire watery globe to swim in" I can't imagine why they'd choose to hang out in sewage.

Again I don't think it's impossible for these resident bacteria to have come from humans, just quite a lot less likely than other sources. My issue with this was that natural sources were not even considered.
 

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Re: Can antibiotics affect sharks?
« Reply #3 on: 06/04/2011 00:50:46 »

 

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