嗜肺性退伍軍人菌加熱與加氯殺菌效能評估

Abstract

Legionella. pneumophila在自然界中分佈甚廣，建築體中也容易大量孳生，尤其辦公大樓、工業場所冷卻水塔與醫療院所冷熱水系統，都是L. pneumophila的可能滋生源，因此以控制水中L. pneumophila的生長，降低感染可能性，是防止退伍軍人症感染的主要方法 本研究建立加熱及加氯殺菌系統，並進行殺菌效能評估。結果顯示，L. pneumophila在60℃與0.5 mg/L 自由餘氯劑量下皆快速失去可培養力。低劑量(0.5 mg/L) 自由餘氯可使細胞膜完整之細菌減低至5 %以下，且總蛋白質大量減少。然而高溫殺菌後仍有5-40 %細菌保持細胞膜完整且總蛋白質量不受影響。當溫度又回復至37℃後，細胞膜完整之細菌比率亦有上升的可能，加氯殺菌後則無此現象。針對蛋白質表現分析，加熱殺菌後與壓力抵抗相關之蛋白質的表現量上升，尤其侵犯宿主之相關蛋白質在長時間加熱後表現量上升，代表細菌在高溫加熱後仍然存活，且欲以感染宿主作為環境壓力抵抗之可能機制。 上述結果顯示加氯殺菌對L. pneumophila控制效果優於加熱殺菌。根據目前的研究結果，建議在控制非飲用水時採用加氯法，而對熱水供應系統以加熱法為控制時，另需定期以不同指標監控環境中L. pneumophila分佈情形，以達到防治退伍軍人症的目的。

Legionella pneumophila is widely spread in both natural and man-made environment. The cooling tower of office buildings and the drinking water of hospitals are both likely to habit L. pneumophila. In order to protect the workers from L. pneumophila infection, it is necessary to eliminate or inhibit the growth of L. pneumophila in aquatic environment. In this study, we evaluated the effectiveness of heat and chlorine disinfection. The culturability of L. pneumophila was lost rapidly under the disinfection condition of 60℃ and 0.5 mg/L free chlorine. The membrane integrant cell percentages were reduced down to 5 % when treated with 0.5 mg/L free chlorine and protein mass was reduced substantially. However, 5~40% cells remained membrane integrant after heat disinfection at 60℃ and 70℃ for 30 min while protein mass was not affected. As incubation temperature back to 37℃, there is a possibility for percentage of membrane integrant cells to increase after heat disinfection. In contrast, no similar observations were found in chlorine-disinfected L. pneumophila. As for protein profile of the heat-disinfected L. pneumophila, host-invasion related proteins were particularly up-regulated in 24 hr heating, implying the survival and infectious potential for the long-term heat disinfected L. pneumophila. Based on the above results, chlorination is better than heating terms of the disinfection efficiency on L. pneumophila. To control L. pneumophila in environments, it is suggested to apply chlorination as the disinfection strategy for the non-potable water system. The route surveillance with non-culture assay methods (e.g., Polymerase Chain reaction) should be performed for L. pneumophila examination in the hot water supply system when the heat treatment is served as the control method.