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I know that antibiotics usually have properties affecting specifically bacterial cells, like by inhibiting peptidoglycan synthesis. but do any antibiotics exist affecting eukaryotic cells, like yeast or other fungi? I read in a text that "most" eukaryotic cells are resistant against antibiotics and that confused me.

Regardless of whether it can be used against bacteria or not, is there any kind of antibiotic effective against fungi, or any kind of eukaryotic cell?

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  • $\begingroup$ Please be more clear. Are you asking if there's any antibiotic usually used against bacteria who's effective also for eucaryotic cells? $\endgroup$ – Shred Jun 17 '18 at 16:26
  • $\begingroup$ No, regardless of whether it is/can be used against bacteria or not. I know that the antibiotics usually have properties affecting specifically bacterial cells like by inhibiting peptidoglycan synthesis. but do any antibiotics exist affecting eukaryotic cells? like yeast? or fungi? I read in a text that "most" eukaryotic cells are resistant against antibiotics. that confused me $\endgroup$ – Taylan Jun 17 '18 at 17:30
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The term antibiotic typically refers to chemicals effective against bacteria. There are antimicrobial chemicals effective against fungi, and they are rather aptly called antifungals.

In general, for every organism, there will be a chemical that is toxic to it.

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  • $\begingroup$ Good answer, but just one suggestion. Wikipedia's definition doesn't match the use of these terms in infectious disease medicine and pharmacology. Antibiotic (like antimicrobial) is a general term (see Goodman and Gilman Chapter 48, General Principles of Antimicrobial therapy). We have more antibacterial antibiotics, in general, since these pathogens are easier to selectively target, so most antibiotics are antibacterial antibiotics. For that reason, yes, it typically refers to chemicals effective against bacteria, but that's just because there are more of them. $\endgroup$ – De Novo Aug 9 '18 at 2:09
  • $\begingroup$ Wikipedia can be a good source, but it is particularly weak for infectious disease principles. $\endgroup$ – De Novo Aug 9 '18 at 2:10
  • $\begingroup$ @DeNovo Wikipedia was not my source, I just included those links for further reading. In my field, antibiotic and antibacterial are used synonymously. The WHO and ECDC seem to agree on this. That said, I'm not a medical doctor nor a pharmacist. I don't disagree with your points and you're welcome to edit my answer as you see fit, or post your own. $\endgroup$ – canadianer Aug 9 '18 at 3:09
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Yes. The antibiotic (general microorganism “targeter”) you’re looking for is an antifungal. There are fewer ways to target fungi as opposed to bacteria, but we can target them nonetheless.

The fungal cell membrane has ergosterol to regulate its permeability whereas the mammalian cell relies on cholesterol. Fungi have cell walls which are not present in mammalian cells and are different in chemical composition to bacterial cell walls. A fungal cell wall is made of chitin whereas, as you mentioned before, a bacterial cell wall is made up of peptidoglycan.

We rely on these differences to target fungi. Some antifungals bind to ergosterol (e.g. Polyenes like Amphotericin-B) whereas other agents inhibit ergosterol synthesis altogether (e.g. Azoles like Triazole). Other antifungal agents target the fungal cell wall by inhibiting the synthesis of chitin (e.g. Echinocandins like Caspofungin).

There are more ways to target fungi, like introducing nucleotide analogues (“look alikes” that don’t work) to disrupt their nucleic acid synthesis (e.g. Fluorocytosine 5-FC). Another method is to disrupt the fungal microtubule’s aggregation during mitosis (e.g. Griseofulvin), thus “arresting” the fungal cells in metaphase.

Recommended Textbooks:

  1. Hugo & Russell’s Pharmaceutical Microbiology 8th edition, Wiley- Blackwell. Edited by S.P. Denyer et al. ISBN 9781444330632

  2. Essential Microbiology for Pharmacy and Pharmaceutical Science, Wiley- Blackwell. By Geoffrey Hanlon and Norman Hodges ISBN 978-0-470-66534-3 (pbk.)

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Yes, there is. The Azole class of drugs, for example, are used to treat (eukaryotic) fungal infections. One such drug is clotrimazole which targets cytochrome p450 which is responsible for the synthesis of ergosterol (a mimetic of cholesterol; not found in humans), ultimately leading to excessive fluidity in fungal membranes and their lysis.

https://www.ncbi.nlm.nih.gov/pubmed/3288361

Its not that eukaryotes are inherently resistant to antibiotics; rather, its often difficult to treat serious eukaryotic infections because humans are also eukaryotes and share similar biochemistries. See below. The problem with clotrimazole is that, although ergosterol is not found in human, the cytochrome p450 is (i.e. in the ETC) and it serves other functions which may be affected.

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