紫外線控制感染性生物氣膠之效能評估

Abstract

金黃色葡萄球菌（Staphylococcus aureus）、綠膿桿菌（Pseudomonas aeruginosa）以及嗜肺性退伍軍人菌（Legionella pneumophila）為造成院內感染之致病菌，而空氣中含有致病性之生物氣膠，經人體吸入後可導致肺囊性纖維化（Cystic fibrosis, CF）或是引發退伍軍人症（Legionnaires’ disease）。因此，需有效控制感染性生物氣膠以避免民眾或工作人員之感染風險。紫外線照射殺菌（Ultraviolet germicidal irradiation, UVGI）為一可有效控制空氣中病原菌之技術，但受空氣中相對濕度（Relative humidity, RH）之影響，且對不同病原性細菌有不同之效應，而目前對S. aureus、P. aeruginosa與L. pneumophila之作用所知有限。因此本研究於實驗室內建置生物氣膠UVGI評估系統，透過AGI-30採樣（10與30分鐘）與培養法分析，探討S. aureus、P. aeruginosa與L. pneumophila在不同RH（12.7-90%）以及UV暴露下之UVGI效能。 結果發現，在未開啟紫外燈時，UV元件內之旋轉作用力可導致生物可培養濃度下降，P. aeruginosa與L. pneumophila下降程度分別為0.7-1.5 log值（80-96.8%）與0.6-1.7 log值（74.9-98%），顯著大於S. aureus為 0.2-0.6 log值（37-74.9%）（p < 0.05）。且對P. aeruginosa與L. pneumophila而言，滯留於UV元件之時間增長時，可培養濃度log下降值也顯著增加（p = 0.0009與p < 0.0001），至多達2倍。 UVGI殺菌效能評估方面，使用UV劑量範圍為7,140-171,632 μW/cm2，而當RH自12.7-16.7%增加至87.3-90%時，S. aureus、P. aeruginosa與L. pneumophila之UVGI效能分別從下降4-4.9 log值（99.99-99.999%）降至1.7-3.1 log值（98-99.9%）、4.4-4.9 log值（99.996-99.999%）降至2.3-3.8 log值（99.5-99.98%）以及3.7-4.3 log值（99.98-99.995%）降至2.2-3.6 log值（99.4-99.97%），與RH呈統計顯著之負向關係（r = -0.81~-0.74）（皆p < 0.0001)。而S. aureus、P. aeruginosa與L. pneumophila之幾何平均氣動粒徑（0.65-0.7 μm、0.62-0.65 μm與0.59-0.7 μm）亦隨RH增加而增加（r = 0.55~0.72)（皆p < 0.0001）。另外，當UV暴露時間自8.1秒增至13.6秒時，S. aureus、P. aeruginosa與L. pneumophila之UVGI殺菌效能亦顯著上升，呈現劑量效應關係（p = 0.002、0.074與0.0009)。在菌種別部份，合併中RH（58.7-59.6%）與高RH（87.3-90%）之UVGI殺菌效能數據觀之，以對S. aureus效能顯著小於對P. aeruginosa與L. pneumophila之影響(p < 0.05)；然於低RH(12.7-16.7%)時以對L. pneumophila之殺菌效能最差(p < 0.05)。另外，採樣10分鐘所得之UVGI殺菌效能高於採樣30分鐘者，且以對L. pneumophila較具影響性（p = 0.064）。由於增加採樣時間可使菌種培養濃度下降，因而造成提高UVGI效能之假象，故在評估UVGI殺菌效能時，應選擇適當之採樣時間以避免錯誤評估。 總結來說，在UVGI殺菌效能評估中，以RH與UV暴露劑量為最重要影響因子（p < 0.0001與p < 0.0001），其次為採樣時間與菌種（p = 0.012與p = 0.07）。由於RH增加導致S. aureus、P. aeruginosa與L. pneumophila之UVGI效能下降，故當應用UVGI殺菌法於室內場所時，應妥適控制RH（< 60%）以達有效殺菌效果。

The nosocomial transmission of Staphylococcus aureus, Pseudomonas aeruginosa and Legionella pneumophila could induce cystic fibrosis or Legionnaires’ disease through inhalation aerosolized pathogens in the hospital.Therefore, it is important to reduce airborne pathogens in the environments in order to ensure workers and the publics’ health. Ultraviolet germicidal irradiation (UVGI) systems were used to control airborne pathogenic organisms. In response to the limited data available regarding the relationship between relative humidity (RH) and UV inactivation of airborne pathogenic organisms, we attempted to evaluate UVGI effectiveness of different RH, UV exposure doses and airborne pathogenic organisms of S. aureus, P. aeruginosa and L. pneumophila in a laboratory chamber setting with AGI-30 for 10 and 30 min by culture assay. Our results indicated that log reduction of P. aeruginosa and L. pneumophila were 0.7-1.5 log unit (80-96.8%) and 0.6-1.7 log unit (74.9-98%) greater than S. aureus were 0.2-0.6 log unit (37-74.9%) (p < 0.05) by swirling motion at UV-off setting. In addition, when the time of bioaerosol remain in UV unit was increase then the log reduction of P. aeruginosa and L. pneumophila was increased as high as 2 times at UV-off (p = 0.0009 and < 0.0001, respectively). In regard to UVGI effectiveness, the UVGI dosage ranged were 7,140-171,632 μW/cm2, it was observed that germicidal efficiency decreased from RH 12.7-16.7% to RH 87.3-90% of S. aureus, P. aeruginosa and L. pneumophila were 4-4.9 log unit (99.99-99.999%) to 1.7-3.1 log unit (98-99.9%), 4.4-4.9 log unit (99.996-99.999%) to 2.3-3.8 log unit (99.5-99.98%) and 3.7-4.3 log unit (99.98-99.995%) to 2.2-3.6 log unit (99.4-99.97%), respectively (r = -0.81~-0.74) (all p < 0.0001). In addition, aerodynamic diameter increase as RH increases for S. aureus, P. aeruginosa and L. pneumophila (0.65-0.7 μm, 0.62-0.65 μm and 0.59-0.7 μm) (r = 0.55~0.72) (all p < 0.0001). Moreover, UV exposure time was from 8.1s to 13.6s with increasing UVGI effectiveness for S. aureus, P. aeruginosa and L. pneumophila in a dose-response matter (p = 0.002, 0.074 and 0.0009, respectively). Significantly, the microorganism susceptibilities by UVGI of P. aeruginosa and L. pneumophila were greater than S. aureus at moderate (58.7-59.6%) and high RH (87.3-90%) (p < 0.05). However, the microorganism susceptibilities by UVGI of L. pneumophila were the lowest at low RH (12.7-16.7%) (p < 0.05). On the other hand, it was found that 30-min sampling was significantly greater than 10-min for L. pneumophila by UVGI effect (p = 0.064). The longer sampling time results in the higher vulnerability of culturable cells, not because of the increasing of the UVGI efficiency. In conclusion, UVGI effectiveness strongly depends on RH and UV exposure doses (p < 0.0001 and p < 0.0001), followed by microorganism species and sampling time, which were weakly relationship with UVGI effectiveness (p = 0.012 and p = 0.07). It was observed that germicidal efficiency decreased as RH increased in S. aureus, P. aeruginosa and L. pneumophila. Our study suggests that RH have a great effect on UVGI efficacy. Therefore, the RH should be maintained lower than 60% in order to higher the germicidal effectiveness, when the UVGI systems are applied in the indoor environments.