醫療廢棄物高溫高壓滅菌處理效能評估之研究

中國醫藥大學機構典藏 China Medical University Repository, Taiwan > 公共衛生學院 > 環境醫學研究所(已停用) > 博碩士論文 > Item 310903500/658

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题名:	醫療廢棄物高溫高壓滅菌處理效能評估之研究
作者:	梁永政;Yung-Cheng Liang
贡献者:	中國醫藥大學：環境醫學研究所碩士班
关键词:	醫療廢棄物;高溫高壓滅菌法;快速判讀生物指示劑;菌落數檢測;medical waste;steam sterilization;rapid readout biological indicator;heterotrophic plant count
日期:	2007-06-08
上传时间:	2009-08-11 16:56:38 (UTC+8)
摘要:	我國醫療廢棄物大多採專用焚化爐焚化處理，但由於該廢棄物含氯量高，加上專用焚化爐規模小操作不穩定，使得戴奧辛排放係數為一般混燒焚化爐的40 ~ 60倍。另外清運過程必須全程保持低溫 (4 ℃)，使得清運處理成本較高 (30~50 NT/kg)。目前國際趨勢朝向現地滅菌解碼後，併入大型垃圾焚化爐或掩埋處理。我國雖已有法源基礎，但目前全國僅3%的醫療廢棄物採用滅菌處理，可能原因為國內缺乏滅菌處理技術及效能查核準則，導致後續處理單位質疑滅菌成效。目前美國已廣泛使用3M快速判讀生物指示劑(rapid readout biological indicator, RRBI ) 進行滅菌效能評估，但由於RRBI不同型號有不同適用條件，易使操作人員混淆，因此本研究以問卷調查台灣醫院使用RRBI之現況，發現受訪醫院31組高溫高壓滅菌鍋中，錯用RRBI比例達16.1 %。本研究進一步使用121 ℃重力式滅菌鍋，以及部份滅菌的操作時間進行試驗，探討RRBI快速判讀 (1~3 hr) 及顏色判讀 (24~48 hrs) 的一致性，並評估錯用RRBI對判讀結果的影響。試驗結果顯示，正確選用RRBI (Attest 1292) 時，兩種判讀一致性達75.3% (n = 150)，而錯用RRBI (Attest 1291) 兩種判讀一致性降至40.7 % (n = 150)，並出現59.3 % 的偽陰性。在滅菌效能評估方面，本研究使用121G (重力模式、121 ℃、60分鐘) 及135V (真空模式、135 ℃、45分鐘) 兩種操作條件進行試驗，並使用四種判讀方式 (螢光、顏色、化學及菌落計數) 評估滅菌效能 (performance evaluation)，以實證包封程度對滅菌效能的影響。試驗時將團狀報紙及空針筒填充於滅菌用塑膠袋中，以模擬機組75%之填充率，而在袋內 (IB)、針筒內 (IBN) 及袋外 (OB) 各放置2支Attest 1292 RRBI及3支1243 Chemical Indicator (CI) 進行滅菌，兩種滅菌操作條件各進行4重複試驗，滅菌後1支BI進行快速及顏色判讀，另1支BI則以菌落數檢測法 (HPC) 計數殘餘菌落計算log kill值。結果顯示在121G試驗中，OB、IB及IBN三種判讀方式的陽性比例分別為0%、75%、75%，OB的log kill平均值達5.0，已符合法規之標準，而IB及IBN的平均值則降至1.7以下，證實121G的滅菌效能易受包封 (塑膠袋及針筒) 所影響；在135V方面，OB、IB及IBN三種判讀方式的陽性比例均為0%，且其log kill平均值皆>5，可見135V較能克服包封的蒸氣阻絕。本研究證實四種效能檢測方式結果相當一致，並發現RRBI判讀陰性時未必符合法規標準，可能原因為快速判讀過快或BI原始菌落數不足所導致，本研究建立BI偵測極限與最低原始菌落之系統分析，並建議後續進一步研究RRBI之適法性。 Incineration at specially permitted sites is currently the major treatment method for medical wastes in Taiwan. This poses a problem of dioxin emission with a high emission factor of 40 ~ 60 times higher than for the mass-burn incineration of domestic wastes due to high chlorine content in wastes and unstable operation associated with relatively small throughput. Moreover, transportation of medical wastes is costly (30~50 NT/kg) because of the requirement of storage at a low temperature of 4 oC. The treatment practice is therefore moving toward non-incineration such as steam sterilization to decode the waste classification followed by mass-burn incineration or landfill. Although regulation has been promulgated in Taiwan for steam sterilization for years, only 3% prefer the non-incineration method, probably due to lack of a technical guideline and audit system to gain the trust from publics. The rapid readout biological indicator (RRBI) manufactured by 3M Co. has been widely accepted as a performance evaluator in USA. However there are several types of RRBI and their test conditions may be confusing. This study conducted a national survey in Taiwan and concluded that RRBI had been incorrectly used at a rate of 16.1% (n = 31). The consequence of misuse was further evaluated with a bench-scale test at 121 oC by partial sterilization of gravity displacement and measured by rapid readout (1~3 hr) followed by color change (24~48 hrs) for confirmation. The results showed a conformance rate of 75.3% (n=150) between the two types of measurement for correct use (Attest 1292) and 40.7% (n=150) for incorrect use (Attest 1291). This suggests a false-negative rate of 59.7% (n=150) when an incorrect type of RRBI is used. Performance evaluation was also conducted using a commercial-scale steam sterilizer with four types of measurement (rapid readout, color change, chemical indicator, and plate count). The purpose was to evaluate the effect of steam barrier on sterilization at two operating conditions of 121G (121 oC for 60 minutes with gravity displacement) and 132 V (132 oC for 45 minutes with vacuum). Scrambled newspaper and empty syringe was packed inside the waste bags and used to achieve a filling ratio of 75% in the autoclave. Two of Attest 1292 and 3 of 1243 chemical indicator (CI) were placed in each of the three test models: inside bag (IB), inside bag and needle (IBN) and outside bag (OB) to simulate different degree of steam barrier. Four replicates were conducted for the performance test. After completion of the operation, one RRBI was measured by rapid readout followed by color change and another underwent the heterogeneous plate count (HPC) procedure to obtain the Log kill estimate. The results showed that 121G test gave a positive ratio of 0%, 75%, and 75% for the three test models of OB, IB, and IBN, respectively, according to the three types of BI measurements. The average log kill reached an acceptable magnitude of 5.0 for OB but was reduced to 1.7 or less for both IB and IBN, suggesting a serious steam barrier problem was encountered due to containerization of the bag and needle. However, no steam barrier was observed for 135V with a positive ratio of 0% and log kill >5 for all the three test models. Accordingly, it is suggested that 135V must be used to avoid the steam barrier problem. Results of the four types of measurement are all in agreement to each other. However, a false negative rapid readout is possible due to inadequate incubation time and/or inadequate level of initial microbial density. Theoretical analysis was performed in this study but laboratory work remains to be studied.
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