大台北都會區車輛雨刷水之退伍軍人菌污染調查

Abstract

過去文獻指出職業駕駛或長時間開車者有較高的退伍軍人病感染風險，而暴露來源可能為車體雨刷水系統遭退伍軍人菌污染，且添加雨刷精之車輛使用者的感染風險顯著較低，然目前缺少詳細的暴露調查數據。研究目的除了評估及定量車輛中之雨刷水其退伍軍人菌污染狀況，另收集相關影響因子，以探討「水質條件」、「車體資訊及用車習慣」和「雨刷水操作維護」如何影響雨刷水中退伍軍人菌檢出及孳生。本研究於台北大都會地區以立意採樣方式，採集民眾自用車及計程車中的雨刷水桶內及其雨刷水出水口的水樣，除進行培養法分析外，並以聚合酶連鎖反應搭配核酸染劑定量樣本中活性及總退伍軍人菌濃度。 在59輛的研究對象中，雨刷水中之總退伍軍人菌屬陽性檢出率介於90.4%-98.3%，陽性樣本之濃度介於3.8 x 101 - 1.9 x 108 cells/mL，而總嗜肺性退伍軍人菌陽性檢出率為75.4%-78.9%；陽性樣本之檢出濃度介於5.7 x 100 – 7.6 x 103 cells/mL；活性方面，活性退伍軍人菌屬陽性檢出率介於88.5%-94.7%，其陽性樣本濃度介於4.9 x 100 - 1.8 x 108 cells/mL，而活性嗜肺性退伍軍人菌陽性檢出率為59.6%-57.9%，陽性樣本之檢出濃度介於1.1 x 101 – 4.0 x 103 cells/mL；在可培養性部分，退伍軍人菌屬陽性檢出率為42.3%-56.1%，但嗜肺性退伍軍人菌只有28.1%-32.7%。計算其雨刷水出水口濃度/雨刷水桶濃度 (O/T)比值大於1，顯示雨刷出水口的Legionella平均濃度較雨刷水桶內高，顯示雨刷水管線可能有Legionella汙染現象。 雨刷水的基質為自來水，比較自來水與雨刷水之水質條件發現自來水之濁度、導電度、總溶解固體 (TDS)、溶解性有機碳 (DOC)與異營性細菌 (HPC) (1.8NTU、87.8μS/cm、41.6 mg/L、小於1ppm和4.4x103 CFU/mL)顯著低於雨刷水 (27.5NTU、382.2μS/cm、204.1mg/L、3259.7ppm和6.2x106 CFU/mL,P=0.02、0.01、0.01、0.01和0.003)，且自來水中總退伍軍人菌屬 (1.9x102 cells/mL)及其活性退伍軍人菌屬 (2.0 x 101 cells/mL)均顯著低於雨刷水 (4.2x106及3.5x106 cells/mL)，約分別為21842和175000倍，顯示雨刷水的水質富含有機營養物質，使其利於退伍軍人菌孳生與存活，因而導致其雨刷水的汙染狀況較自來水嚴重。 以Generalized estimating equation (GEE)分析雨刷水退伍軍人菌污染之影響因子的模式中，總及活性之退伍軍人菌屬的檢出濃度顯著受到硬度負向影響(β=-0.011,P<0.0001和β=-0.01, P=0.001)；在嗜肺性退伍軍人菌方面，硬度亦負向顯著影響總及活性之嗜肺性退伍軍人菌濃度(β=-0.007,P<0.0001和β=-0.007, P=0.01)，另外在導電度越高時，其總及活性嗜肺性退伍軍人菌之濃度也會增高 (β=0.0003, P<0.0001和β=0.0005,P=0.0001)，在模式中亦可發現雨刷清潔劑添加頻率小於每6個月添加1次者其車中雨刷水中總及活性嗜肺性退伍軍人菌的濃度顯著低於添加頻率大於每6個月添加1次者 (β=-0.24,P=0.0013和β=-0.58, P<0.001)，而若欲控制雨刷水中退伍軍人菌汙染時應考量上述危險因子。 在59輛的研究對象中包括計程車輛 (職業駕駛)及民眾自用車 (非職業駕駛)，發現職業駕駛者其車輛平均車齡較非職業駕駛車輛低，由於職業駕駛開車頻率高且開車時數長，加上職業駕駛添加雨刷清潔劑及雨刷水的頻率較高，因而發現在職業駕駛者其車輛雨刷水中總及活性退伍軍人菌屬濃度 (1.5x106和1.9x105 cells/mL)低於非職業駕駛 (4.9x106和4.6x106cells/mL)，顯示在用車頻繁的情況下，能夠定期進行雨刷水操作及維護者，可降低雨刷水中的退伍軍人菌汙染情況。整體而言，本研究發現添加雨刷清潔劑無法完全抑制雨刷水中的退伍居人菌滋生，但其雨刷水的操作維護及用車習慣會影響雨刷水中的退伍軍人菌檢出及孳生。

Previous studies show that occupational drivers infecting Legionnaires’ disease significantly greater than the general population, which is considered to be associated with Legionella contamination in windshield wiper fluid. The use of screen wash seems to reduce the infection risk; however, thorough environmental surveillance is unavailable. The objectives of this study is evaluating the concentration of Legionella in windshield fluids of vehicles and collecting the impact factors of “water quality”, ”information of vehicles” and “maintenance of wiper fluid” to determine how they affect the presence and abundance of Legionella in winper fluid samples.Thus, water samples were collected from the tank and outlet of the windshield wiper system of the vehicles selected in Taipei metropolitan area with purposive sampling. Except of culture assay for culturable Legionella, total and viable Legionella were quantified using quantitative real time polymerase chain reaction (qPCR) coupled with ethidium monoazide. Total and viable Legionella spp. was detected in the range of 90.4%-98.3% and 88.5%-94.7%, for which the range of concentrations were 3.8 x 101 - 1.9 x 108 and 4.9 x 100 - 1.8 x 108 cells/mL, respectively. Total and viable L. pneumophila was detected in the range of 75.4%-78.9% and 59.6%-57.9%, respectively, and the range of concentration was 5.7 x 100 – 7.6 x 103 and 1.1 x 101 – 4.0 x 103 cells/mL. In addition, culturable Legionella spp. and L.pneumophila were detected in range of 42.3%-56.1% and 28.1%-32.7%. In the 59 subjects’ vehicles, Legionella concentration in outlet samples was greater than that in tank samples, indicating that Legionella contamination in their wiper fluid pipeline. Because wiper fluid came from tap water, we compared the water quality between wiper fluid and tap water samples. It indicated that the turbidity, conductivity, TDS, DOC and HPC of tap water (1.8 NTU、87.8 μS/cm、41.6 mg/L、less than 1 ppm and 4.4x103 CFU/mL) is significantly higher than the wiper fluid’s (27.5 NTU、382.2 μS/cm、204.1 mg/L、3259.7 ppm and 6.2x106 CFU/mL,P=0.02、0.01、0.01、0.01 and 0.003). Besides, total and viable Legionella spp. concentration in tap water (1.9x102 and 2.0 x 101 cells/mL) was significantly lower (21842x and 175000x) then wiper fluid (4.2x106 and 3.5x106 cells/mL),respecterly. It indicated that the abounant oraganic materials in wiper fluid which accelerated the propagation and viability of Legionella. Generalized estimating equation (GEE) model analyzed the association between impact factors and Legionella contamination. Total and viable Legionella spp. concentrations were negatively associated with hardness (β=-0.011,P<0.0001和β=-0.01, P=0.001). On the other hand, total and viable L. pneumophila concentrations was increased with conductivity (β=0.0003, P<0.0001和β=0.0005,P=0.0001). Furthermore, the total and viable L. pneumophila concentrations in wiper fluid samples which were added detergent solution below every six months was significantly lower than the vehicles which were adding detergent solution over every six months (β=-0.24,P=0.0013 and β=-0.58,P<0.001).These risk factors should be considered in the control of Legionella contamination in wiper fluid. In this study, Professional driver’s vehicle age was younger than non-professional driver. Besides,the frequency of adding detergent soluntion in professional drivers were higher than non-professional drivers ; it might associated with high driving frequency and average driving time per day of professional drivers. Therefore, it found that total and viable Legionella spp. concentration in professional driver’s wiper fluid (1.5x106 and 1.9x105cells/mL) was lower than the non-professional driver’s (4.9x106 and 4.6x106cells/mL, p=0.13 and 0.07). In conclusion, even in the high driving frequency condition, the proper and frequent maintenance for wiper fluid might decrease the contamination of Legionella. Moreover, adding screen wash in windshield cound not significantly inhibit the growth of Legionella, but the habit of vehicle use and maintenance of wiper fluid could affect the presence and abundance of Legionella in wiper fluid samples.