Inactivation of Cryptosporidium using ultraviolet and radioactive reys

为确定不同温度和强度下灭活微小隐孢子虫卵囊的效果，进行了不同温度和强度的辐射灭活试验研究。随着辐射剂量的增加，传染性呈指数下降。导致2log_lt；10&gt；传染性降低的伽马射线剂量和β射线剂量分别为94GY和92GY。温度和强度对射线照射降低卵囊感染力的效果无显著影响。用体外激发法评估2log_&lt；10&gt；减少存活率所需的伽马射线剂量和β射线剂量分别为13,000和12,000射线。因此，辐射处理后的卵囊能够长出卵囊，但不受感染。研究了照射后的卵囊通过光复活和暗修复恢复感染性的可能性。经荧光光照射或在黑暗中储存后，感染性仍未恢复。U-…的疗效对胡敏素与卵囊均匀混合的卵囊悬浮液进行更多的单位剂量的V照射，几乎与在纯水中对卵囊悬液的照射一样高。这表明，即使紫外光穿过混浊的液体，单位剂量的紫外光照射的有效性仍然没有改变。我们的结果还表明，胡敏素与卵囊壁的黏附没有明显的屏蔽作用。对于不附着于卵囊壁的高岭土，UV照射对微小隐孢子虫卵囊悬浮液的作用略强于对卵囊悬浮液的照射。因为效力的增加可以忽略不计，但是我们没有研究这种增加是否是由于高岭土颗粒对紫外光的散射所致。有一种趋势是，高岭土与卵囊壁的粘附会导致钝化作用的减少，胡敏素的粘附性也是如此。然而，无论是用激发试验还是用小鼠感染性试验，高岭土在黏附过程中的对数失活幅度都仅比纯水中小约10%。较少

Experimental studies on radioactive rays irradiation were conducted to determine the efficacy of inactivating C. parvum oocysts at various temperatures and intensities. The infectivity decreased exponentially as radiation doses increased. The gamma ray and beta ray doses resulting in a 2 log_<10> reduction in infectivity were 94 Gy and 92 Gy, respectively. Temperature and intensity did not significantly affect the efficacy of radioactive rays irradiation in reducing the infectivity of oocysts. Gamma ray and beta ray doses required for 2 log_<10> reduction in viability as evaluated using in vitro excystation were 13,000 Gy and 12,000 Gy, respectively. Thus, radioactive ray treatment resulted in oocysts that were able to excyst but not infect.The potential of irradiated oocysts to recover infectivity by photoreactivation and dark repair was investigated. There was no recovery in infectivity following treatment by fluorescent-light irradiation or storage in darkness.The effectiveness of U … More V irradiation per unit dose towards an oocyst suspension where humin was mixed homogeneously with the oocysts, was nearly as high as that towards an oocyst suspension in pure water. This indicates that even though the UV beam passed through a turbid fluid, the effectiveness of UV irradiation per unit dose remained unaltered. Our results also suggest that the adhesion of humin to the oocyst wall has no marked shielding effect. As to kaoline which does not adhere to the oocyst wall, UV irradiation was slightly more potent towards C. parvum oocyst suspensions in water containing kaoline than towards oocyst suspensions in pure water. Because the increase in potency was negligible, however we did not study whether the increase resulted from scattering of the UV beam by kaoline particles. A trend was noted that adhesion of kaoline to the oocyst wall resulted in a decrease in inactivation as did adhesion of humin. However, the magnitude of log_<10> inactivation during adhesion of kaoline was only about 10% less than that in pure water irrespective of whether assessment was made by excystation assay or by mouse infectivity assay. Less