Bacteria

[Squidward]

Hi All,

What is the difference between gram negative & gram positive bacteria?

Thanks
Squidward

 

[Bignose]

It is an old nomenclature that really depended on whether a strain of bacteria would be colored by a certain stain or not. It has to do with the structure of their cell membrane. Because some medications go through the cell membranes in a way similar to the stain, it can be important as to which type of bacteria you are trying to treat with what kind of medicine. Usually though, just using a broad spectrum medicine is the best bet, since it usually isn't straightforward to determine the exact type of bacteria you are trying to eradicate.

 

[Squidward]

It is an old nomenclature that really depended on whether a strain of bacteria would be colored by a certain stain or not. It has to do with the structure of their cell membrane. Because some medications go through the cell membranes in a way similar to the stain, it can be important as to which type of bacteria you are trying to treat with what kind of medicine. Usually though, just using a broad spectrum medicine is the best bet, since it usually isn't straightforward to determine the exact type of bacteria you are trying to eradicate.

Bignose,
Thanks for explanation.
I see though that these terms are widely used.

 

[Skins]

It is an old nomenclature that really depended on whether a strain of bacteria would be colored by a certain stain or not. It has to do with the structure of their cell membrane. Because some medications go through the cell membranes in a way similar to the stain, it can be important as to which type of bacteria you are trying to treat with what kind of medicine. Usually though, just using a broad spectrum medicine is the best bet, since it usually isn't straightforward to determine the exact type of bacteria you are trying to eradicate.

Which "broad spectrum medicine" would you recommend?

Keith.

 

[saltynay]

Tea tree if you can mix it yourself or Melafix if you want it to be simple (same thing just premixed to make it more water soluble)

 

[Bignose]

I like Maracyn Plus. Maracyn does the gram-positive, Maracyn-Two does the gram-negative, and Maracyn Plus does both. It is a very powerful antibacterial that kills quite a lot. Melafix is good for light infections, because it is a relatively weak anti-bacterial. I have only had to use anti-bacterials one time, however, when I first got fish and they had a nasty infection of gill flukes. It took me a while to correctly diagnose what they were.

I first treated the fish for ich, and that helped, but didn't eliminate the flicking issues.

Then I thought it may be bacterial, so the fish got a healthy dose of Maracyn Plus.

Finally, I gave them a dose of praziquantel and that cured it right up. Praziquantel is a very effective fluke killer, so I think that it was pretty clearly gill flukes or similar that my fish were. The nice thing about prazi is that it is practically impossible to overdose, so whenever I bought fish from that shop, I put them into quarantine and give them a large dose of prazi. I've never had a disease problem since.

 

[Squidward]

Am I correct in saying you can't use Melafix if there are Gouramis in the tank?

 

[twodoctors]

Gram positive and negative as mentioned above is related to how it would stain by Gram staining. Nothing to do with how virulent the bacteria is.

With regards to antibiotics, there is no strong or weak antibiotics. Only correct or incorrect ones. A broad spectrum antibiotics kills a lot of different kind bacteria, but because they are widely used, the bacteria build up resistant to these, so they become less effective (or ineffective). Good example in real life is Penicillin.

Fluke is not a bacteria, so antibiotics don't work on them.

I have no knowledge in fish microbiology, so I can't comment on which antibiotics is best for which bugs.

Adrian

 

[raptorrex]

if you are in the UK, you will need to visit a vet to get these drugs. nobody should consider using them, unless they do so.

 

[Bignose]

With regards to antibiotics, there is no strong or weak antibiotics. Only correct or incorrect ones.

I am really not sure what you are saying here. Because some antibacterials are more effective at killing bacteria than others. In common terms, this is usually referred to as "strong". Also, the amount of antibacterial activity is going to be dose and concentration dependent. So, a medicine can also be considered "strong" or "weak" depending on how concentrated the medicine is for a prescribed dose.

So, maybe I am misunderstanding, but I don't see how "there is no strong or weak".

 

[Bignose]

As a follow up, look at the wording of the wikipedia article for Erythromycin: http/en.wikipedia.org/wiki/Erythromycin

Erythromycin is a macrolide antibiotic that has an antimicrobial spectrum similar to or slightly wider than that of penicillin

Clearly the how wide of an antimicrobial spectrum is at least one measure of how strong or weak an antibacterial agent is. A stronger one would have a wider spectrum than a weaker one.

 

[drunkenmonkey]

The difference between Gram Positive and Gram Negative bacteria is based on the results of Gram staining... In general, Gram Positive bacteria will retain crystal violet dye while Gram Negative bacteria will not.

Gram Positive bacteria have a different outside structure... they only have one outer membrane (think skin) with a thick layer of PG (=peptidoglycan... basically sugar + protein structure).

Gram Negative bacteria have a very thin layer of PG but also have an additional outer member. This membrane is rather hydrophilic, meaning it can protect the bacteria from potentially harmful drugs or detergents. So Gram Negative bacteria generally have a wider range of antibiotic resistance compared to Gram Positive bacteria.

Certain antibiotics are more effective against some types of bacteria because of their specificity. Broad spectrum antibiotics tend to affect most bacteria because they target something universally conserved among all bacteria. One example would be interfering with DNA replication, and hence bacterial growth.

Narrow spectrum antibiotics will affect bacteria that belong to a certain group. As a result, they are highly effective against certain types of bacteria, while having minimal effects against others.

It's like a jack-of-all trades VS specialist. Broad range will be able to affect more types of bacteria while narrow range will affect a certain subset of bacteria.

There is no "better" antibiotics... We generally use broad spec ABs for infections that we cannot characterize. Ideally, we would determine the pathogenic bacteria and select a narrow spec AB that will target it specifically.

Having said all this... Maracyn Plus is nice because it affects G+ and G- bacteria.

ps first post here after like 7 years of inactivity.