水樣濁度對以免疫磁性分離法進行隱孢子蟲孢囊檢測回收率之影響

Abstract

隱孢子蟲是一種寄生性之原生動物，主要寄生在人類、鳥類和多種哺乳類腸道內，當隱孢子蟲脫離宿主會成為孢囊來抵抗環境。孢囊以糞口傳染作為感染途徑，受到感染的宿主會導致隱孢子蟲症，以水作為孢囊傳播媒介，因此容易爆發大流行，美國曾經在1993年發生過40萬人遭受感染的大流行。目前水廠消毒單元並無法有效抑制孢囊生長，仍以砂濾池作為去除孢囊之最後一道防線。除了持續監測出流水中孢囊存在的可能性外，反沖洗廢水中孢囊含量亦會影響混凝之加藥量。因此，有效掌握反沖洗廢水中孢囊數目可提供水廠作為反沖洗水再利用之重要參考依據。目前普遍用來分離隱孢子蟲孢囊之方法為免疫磁性分離法 (IMS)，其利用抗體抗原之專一性反應，可有效捕捉到孢囊與雜質分離。因此，針對反沖洗廢水之濁度和高濃度孢囊存在的問題，本研究進行濁度對隱孢子蟲孢囊檢測回收率影響之探討。

首先在純水條件中找出0.1N HCl破壞鍵結之最佳操作條件，實驗結果發現，混合時間30秒，混合3次，可得到完整孢囊數目。另外，以高嶺土製備人工濁水，以純水條件所得到0.1N HCl混合之最佳參數，進行濁度對於隱孢子蟲孢囊檢測回收率影響之探討。結果發現，適當的濁度 (0.5 NTU)會促進孢囊檢測回收率，當濁度大於0.5 NTU後，孢囊檢測回收率隨濁度增加所而逐漸下降，尤其當濁度為10~40 NTU最為明顯 (R2=0.999)。最終利用濃縮程序之離心力、離心時間、磁珠添加劑量和原水稀釋來改善濁度水體之孢囊檢測回收率，結果發現，原水稀釋可有效將濁度水體之孢囊檢測回收率提升，表示稀釋可以降低部分濁度干擾，增加磁珠捕捉孢囊效能，尤其在低濁度狀況下較為顯著。此結果亦說明將孢囊與雜質分離，達到有效的濃縮和收集是影響檢測孢囊之相當重要目標。

Cryptosporidium spp. are protozoan parasites which are known to infect the gastrointestinal tract of vertebrates, including humans, birds and mammals. The infection causes the disease cryptosporidiosis which is a life threatening disease to immunocompromised individuals. When Cryptosporidium leaves the host, it forms oocysts to resist environmental hardship, which are transmitted by the fecal-oral route. There have been many waterborne outbreaks world-widely. The most severe incidence occurred in Milwaukee, WI, USA in 1993, where more than 400,000 people were infected.

Chlorine disinfection is ineffective in controlling oocyts in water treatments. Physical removal of oocysts can be accomplished by filtration of a conventional water treatment process, the last barrier to the release of particles and protozoan oocysts into the distribution system. Estimate of oocyst numbers in backwash water provides the reference for backwash water reuse in the water treatment. The currently accepted technique for oocyt isolation from water samples is immunomagnetic separation (IMS). The technique is critically interfered by high number of oocyst and high turbidity.

In this study, we examined the effect of turbidity on recovery of Cryptosporidum oocysts. First, the optimal condition for the bond-breaking of bead-oocyst complex by 0.1N HCl was determined. Secondly, the effect of turbidity on recovery of oocysts in synthetic turbid water was investigated. The presence of suspended particles in the water enhanced the recovery of oocyst, as shown by the highest level of oocyst recovery at 0.5 NTU. The increase in turbidity from 0.5 to 100 NTU led to decreasing oocyst recovery, especially in the turbidity range from 10 to 40 NTU with an r square of 0.999.

Experimental parameters including the force and time of centrifuge in concentration process, Dynalbeads dosage, and dilution of synthetic water were varied to improve the recovery of oocysts by IMS process. Dilution of water samples effectively lower the interference of turbidity and improved the recovery. Isolation of oocyst from water impurities and effective concentration and collection are important steps in the recovery of oocyst.