Ellepola A N, Samaranayake L P
Faculty of Dentistry, University of Hong Kong, Hong Kong.
Oral Dis. 1998 Dec;4(4):260-7. doi: 10.1111/j.1601-0825.1998.tb00290.x.
Postantifungal effect (PAFE) is defined as the suppression of growth that persists following limited exposure of yeasts to antimycotics and subsequent removal of the drug. As there are no data on the PAFE of oral C. albicans isolates the main aim of this investigation was to measure the PAFE of 10 oral isolates of C. albicans following limited exposure (1 h) to five antifungal drugs, including nystatin which has not been previously used in PAFE assays. A secondary aim of the study was to evaluate the biological significance of PAFE, using a nystatin pre-exposed isolate of C. albicans and observing its adherence to denture acrylic surfaces, during the PAFE period.
A total of 10 oral isolates of C. albicans were examined for the presence of the PAFE after 1 h exposure to five antifungal drugs, nystatin, amphotericin B, 5-fluorocytosine, ketoconazole and fluconazole. PAFE was automatically assessed with the help of a Spectramax machine which utilizes the principle of periodic turbidometric assessment of growth rates at a given temperature over a given period. The data thus collected are automatically processed in a graphic format as a computer printout. The PAFE was determined as the difference in time (h) required for growth of the drug-free control and the drug-exposed test cultures to increase to 0.05 absorbance level following removal of the antifungal agent (by repeated washing). The adhesion of the single isolate to denture acrylic following limited exposure to nystatin was assessed by a previously described in vitro adhesion assay.
Significant PAFE were observed for nystatin, amphotericin-B and 5-fluorocytosine. A marginal PAFE was observed for ketoconazole and little or none for fluconazole. The mean duration of the PAFE of nystatin, amphotericin-B, 5-fluorocytosine, ketoconazole and fluconazole were 2.89 (+/- 0.27) h, 2.83 (+/- 0.23) h, 3.18 (+/- 0.31) h, 0.65 (+/- 0.11) h and 0.16 (+/- 0.06) h, respectively. The mean percentage reduction of adhesion of oral C. albicans BU47204 to denture acrylic during the PAFE period following exposure to nystatin for 10, 30, 50, 70 and 90 min was 9.12%, 61.73%, 65.99%, 82.16% and 83.14%, respectively.
These in vitro findings imply that even a short period of exposure to antifungals may result in modulation of the growth and the virulent attributes of C. albicans, which however is largely dictated by the antimycotic agent in question. Whether such mechanisms operate in vivo needs to be clarified by further studies.
抗真菌后效应（PAFE）的定义为，酵母菌在有限时间内接触抗真菌药物并随后去除药物后持续存在的生长抑制现象。由于尚无关于白色念珠菌口腔分离株PAFE的数据，本研究的主要目的是测定10株白色念珠菌口腔分离株在有限接触（1小时）5种抗真菌药物（包括此前未用于PAFE测定的制霉菌素）后的PAFE。本研究的次要目的是，使用一株预先接触制霉菌素的白色念珠菌分离株，并在PAFE期间观察其对义齿丙烯酸表面的黏附情况，以评估PAFE的生物学意义。
共检测10株白色念珠菌口腔分离株在接触5种抗真菌药物（制霉菌素、两性霉素B、5-氟胞嘧啶、酮康唑和氟康唑）1小时后的PAFE情况。借助Spectramax机器自动评估PAFE，该机器利用在给定温度下给定时间段内通过周期性比浊法评估生长速率的原理。如此收集的数据以图形格式自动处理并打印成计算机输出结果。PAFE定义为在去除抗真菌剂（通过反复洗涤）后，无药物对照培养物和接触药物的测试培养物生长至0.05吸光度水平所需时间（小时）的差值。通过先前描述的体外黏附试验评估单一分离株在有限接触制霉菌素后对义齿丙烯酸的黏附情况。
观察到制霉菌素、两性霉素B和5-氟胞嘧啶有显著的PAFE。酮康唑观察到轻微的PAFE，氟康唑几乎没有或没有PAFE。制霉菌素、两性霉素B、5-氟胞嘧啶、酮康唑和氟康唑的PAFE平均持续时间分别为2.89（±0.27）小时、2.83（±0.23）小时、3.18（±0.31）小时、0.65（±0.11）小时和0.16（±0.06）小时。白色念珠菌口腔分离株BU47204在接触制霉菌素10、30、50、70和90分钟后的PAFE期间，对义齿丙烯酸黏附的平均减少百分比分别为9.12%、61.73%、65.99%、82.16%和83.14%。
这些体外研究结果表明，即使短时间接触抗真菌药物也可能导致白色念珠菌的生长和毒力特性发生改变，不过这在很大程度上取决于所使用的抗真菌药物。这种机制在体内是否起作用需要通过进一步研究来阐明。
