# Could Metronidazole build up chytrid resistance to itraconaz



## Roadrunner (Mar 6, 2004)

After recently reading that all azole drugs could possibly be effective treatments for chytrid and also reading that chytrid seems to be building a resistance to itraconazole, I was wondering: could widespread use of metronidazole for possible bacterial or other fungal or protozoal infections in frogs w/out testing if chytrid is the culprit and having chytrid present result in the buildup of a resistance to azole drugs by chytrid?
Say you had a tinc that just adr and fecals show some bacteria and protozoa present. If misdiagnosed as a protozoal infection(when in fact the protozoa are benign) and metro prescribed, when in fact it`s chytrid, could this result in a treatment time short enough to not kill the chytrid but long enough to build a resistant strain?


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## Ed (Sep 19, 2004)

Hi Aaron,

Azoles are a large group of drugs that have different funtions... while I won't rule out metronidazole being a possible item, I suspect other azoles are the reason for the resistance (due to thier function). 

Azole antifungals in this case are imidazoles (see http://en.wikipedia.org/wiki/Imidazole) while metronidazole is a Nitroimidazoles (see http://en.wikipedia.org/wiki/Nitroimidazole) Imidazoles antifungal drugs suppress the ability of the fungus to make ergosterol an important cell component while metronidazole to our knowledge does not affect the fungus in this way so there isn't an pressure on it to develop a resistance to the metronidazole (now this doesn't mean that indiscriminate use of metronidazole won't cause something else to develop resistance...).

Ed


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## elscotto (Mar 1, 2005)

Aaron-
Could you provide the source where you read that "chytrid seems to be building a resistance to itraconazole". 
Thanks- Scott


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## Roadrunner (Mar 6, 2004)

one of ed`s posts I believe.


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## rozdaboff (Feb 27, 2005)

Another point to consider is that Metronidazole is a prodrug that is converted into its active form by a redox enzyme. One of the reasons that metronidazole is so effective in anaerobes is the prevalence of this enzyme. 

There are members of the _Chytridiomycata_ that are anaerobic, but I couldn't find how closely they are related to _B. dendrobatidis_ (the species that causes amphbian chytriodiomycosis). _B. dendrobatidis_ is not an anaerobe, however.

So - if the enzyme is not present, metronidazole will not have an effect.


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