Al-Mohammed Hamdan I, Chance Michael L, Bates Paul A
Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, United Kingdom.
Antimicrob Agents Chemother. 2005 Aug;49(8):3274-80. doi: 10.1128/AAC.49.8.3274-3280.2005.
The sensitivities of Leishmania mexicana amastigote and promastigote forms to amphotericin B were investigated in vitro and found to be strongly influenced by the culture media used. When differences in culture media were minimized, there was no significant difference in the 50% inhibitory concentration values between the two life cycle stages. Stable amphotericin B-resistant amastigote and promastigote lines were produced by the application of increasing drug pressure to long-term cultures. Lines capable of growth in concentrations of amphotericin B lethal to normal parasites were produced. Compared to normal parasites, these amphotericin-resistant lines showed marked differences in membrane sterol compositions, with very high levels of 4,14,dimethyl-cholesta-8,24-dienol and other methyl sterols. They also showed a consistent morphological feature, the presence of multilamellar membrane-like material in the flagellar pocket, revealed by transmission electron microscopy. Amphotericin-resistant parasites were capable of infecting BALB/c mice, but the resulting lesion growth was slower than that after infection with normal parasites. However, unlike normal parasites, the amphotericin-resistant parasites were unaffected by experimental chemotherapy with amphotericin B. These results show that amphotericin B resistance could arise as a result of increased clinical use of amphotericin B therapy.
对墨西哥利什曼原虫无鞭毛体和前鞭毛体形式对两性霉素B的敏感性进行了体外研究，发现其受所用培养基的强烈影响。当培养基差异减至最小时，两个生命周期阶段之间的50%抑制浓度值没有显著差异。通过对长期培养物施加递增的药物压力，产生了稳定的两性霉素B抗性无鞭毛体和前鞭毛体株系。获得了能够在对正常寄生虫致死浓度的两性霉素B中生长的株系。与正常寄生虫相比，这些抗两性霉素株系在膜甾醇组成上表现出明显差异，含有非常高水平的4,14-二甲基胆甾-8,24-二烯醇和其他甲基甾醇。它们还表现出一致的形态学特征，即通过透射电子显微镜观察到鞭毛囊中存在多层膜样物质。抗两性霉素的寄生虫能够感染BALB/c小鼠，但产生的病变生长比感染正常寄生虫后慢。然而，与正常寄生虫不同，抗两性霉素的寄生虫不受两性霉素B实验性化疗的影响。这些结果表明，两性霉素B抗性可能是由于两性霉素B治疗临床使用增加而产生的。
