Polyenes antibiotic-resistance

Nystatin [nye STAT in] is a polyene antibiotic its structure, chemistry, mode of action, and resistance resemble those of amphotericin B. Its use is restricted to topical treatment of Candida infections because of its systemic toxicity. The drug is negligibly absorbed from the gastrointestinal tract, and it is never used par-enterally. It is administered as an oral agent ( swish and swallow ) for the treatment of oral candidiasis. Excretion in the feces is nearly quantitative. Adverse effects are rare because of its lack of absorption, but occasionally nausea and vomiting occur. 

In fungi, increases in sterol content also increases polyene sensitivity when the yeast Schizosaccharomyces faponicus was grown aerobically it contained ergosterol and was sensitive to polyenes, but when grown anaerobically this yeast lacked sterol and became polyene-insensitive [137]. When the sterol level of Candida albicans was increased, this was accompanied by increased antibiotic sensitivity [138]. In yeasts, lowered sterol levels resulted in greater resistance to polyene antibiotics [138,139]. 

It is often stated that resistance to polyene antibiotics does not occur [103, 299—301). It is perhaps more true to say that although yeasts and other fungi are capable of giving rise to polyene-resistant strains, polyene resistance has not become a clinical problem, even after twenty years of therapeutic use. This is fortunate, for an increase in resistance of twenty-fold would be sufficient to render many strains of pathogenic and opportunistic fungi resistant to antibiotic concentrations that can be achieved in clinical lesions by conventional polyene therapy. 

Ion-permeability Increased both In the case of sensitive and non-sensitive cells on the effect of both saponin and polyene antibiotics. The scale of increase does not agree with the scale of sensitivity. This means, that the membrane construction of the cells without active metabolism is not able to compensate the Increased Ion-permeability, not even In the case of the resistant strains. 

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