Melanization of Cryptococcus neoformans and Histoplasma capsulatum reduces their susceptibilities to amphotericin B and caspofungin
Melanization of Cryptococcus neoformans and Histoplasma capsulatum reduces their susceptibilities to amphotericin B and caspofungin
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DOI：
10.1128/aac.46.11.3394-3400.2002
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发表时间：
2002-11-01
影响因子：
4.9
通讯作者：
Nosanchuk, JD
中科院分区：
文献类型：
--
作者：
van Duin, D;Casadevall, A;Nosanchuk, JD
真菌病原菌新生隐球菌和组织胞浆菌在体外和哺乳动物感染过程中，在L-多巴存在下产生黑色素样色素。我们研究了黑化是否影响真菌对两性霉素B、卡泊芬净、氟康唑、伊曲康唑或氟胞嘧啶(5FC)的敏感性。使用美国国家酵母菌临床实验室标准委员会的标准宏观稀释MIC方案(M27A方案)，我们发现黑色化和非黑色化的新生葡萄球菌和囊状芽孢杆菌分离株的敏感性没有差异。杀灭试验表明，黑化降低了这两种真菌对两性霉素B和卡泊芬净的敏感性。与L多巴共培养的乳糖酶缺陷型新生葡萄球菌细胞对两性霉素B或卡泊芬净的杀伤敏感性明显高于同基因黑色素产生酵母。两性霉素B或卡泊芬净与黑素预先孵育会降低它们的抗真菌活性。对与两性霉素B或卡泊芬净孵育的黑色素进行的元素分析显示，黑色素的C/N比发生了变化，这表明这些药物与黑色素结合。相比之下，氟康唑、伊曲康唑或5FC与黑色素的孵育并没有显著影响药物的抗真菌效果或黑色素的化学成分。这一结果可能解释了卡泊芬净在体内对新生葡萄球菌的无效作用，尽管它在体外具有活性。此外，结果表明，真菌黑色素保护新生隐球菌属和胶囊隐球菌属不受两性霉素B和卡泊芬净的影响，这种保护作用不能通过标准的肉汤大量稀释法来证明。
The fungal pathogens Cryptococcus neoformans and Histoplasma capsulatum produce melanin-like pigments in the presence of L-dopa in vitro and during mammalian infection. We investigated whether melanization affected the susceptibilities of the fungi to amphotericin B, caspofungin, fluconazole, itraconazole, or flucytosine (5FC). Using the standard macrodilution MIC protocol (the M27A protocol) of the National Committee for Clinical Laboratory Standards for yeast, we found no difference in the susceptibilities of melanized and nonmelanized C. neoformans and H. capsulatum isolates. Killing assays demonstrated that melanization reduced the susceptibilities of both fungi to amphotericin B and caspofungin. Lactase-deficient C. neoformans cells grown with L-dopa were significantly more susceptible than congenic melanin-producing yeast to killing by amphotericin B or caspofungin. Preincubation of amphotericin B or caspofungin with melanins decreased their antifungal activities. Elemental analysis of melanins incubated with amphotericin B or caspofungin revealed an alteration in the C:N ratios of the melanins, which indicated binding of these drugs by the melanins. In contrast, incubation of fluconazole, itraconazole, or 5FC with melanins did not significantly affect the antifungal efficacies of the drugs or the chemical composition of the melanins. The results suggest a potential explanation for the inefficacy of caspofungin against C. neoformans in vivo, despite activity in vitro. Furthermore, the results indicate that fungal melanins protect C. neoformans and H. capsulatum from the activities of amphotericin B and caspofungin and that this protection is not demonstrable by standard broth macrodilution assays.