Reponen T A, Wang Z, Willeke K, Grinshpun S A
Aerosol Research and Exposure Assessment Laboratory, Department of Environmental Health, University of Cincinnati, Ohio 45267-0056, USA.
Infect Control Hosp Epidemiol. 1999 Apr;20(4):237-41. doi: 10.1086/501618.
The overall aim of this study was to investigate the survival and possible growth of Mycobacterium tuberculosis simulant bacteria on respirator filters.
Mycobacterium smegmatis was used as a biochemical simulant for M tuberculosis. Bacterial survival was tested on National Institute for Occupational Safety and Health-certified N95 respirators from three manufacturers. The first experiments simulated one-time respirator use and subsequent storage for 1 to 9 days under ideal conditions for the growth of mycobacteria: 37 degrees C and 85% relative humidity. The bacteria were loaded on the respirator filters under three different nutritional conditions: in the absence of nutrients; in the presence of human saliva (simulating conditions when the respirator is worn); and in the presence of nutrient broth (for ideal growth potential). The subsequent experiments simulated respirator wear for 2 hours under medium work-load conditions at a breathing rate of 56 L/min.
It was found that M smegmatis did not grow on the tested respirators, even when the respirators were stored at temperature, humidity, and nutrition conditions most favorable for microbial growth. However, these bacteria could survive on respirators for up to 3 days during storage. The culturability of M smegmatis was not affected by airflow that simulated the breathing rate associated with medium work-load conditions for 2 hours.
This study shows that M tuberculosis surrogate bacteria collected on a respirator are not able to grow and are able to survive only in ideal (ie, not clinically relevant) conditions. Based on these experiments, we conclude that M tuberculosis is unlikely ever to become an infectious problem in the air again, once it is removed by a respirator.
本研究的总体目标是调查结核分枝杆菌模拟菌在呼吸器过滤器上的存活情况及可能的生长情况。
耻垢分枝杆菌被用作结核分枝杆菌的生化模拟菌。在来自三个制造商的经美国国家职业安全与健康研究所认证的N95呼吸器上测试细菌的存活情况。首次实验模拟一次性使用呼吸器并随后在有利于分枝杆菌生长的理想条件下（37摄氏度和85%相对湿度）储存1至9天。在三种不同营养条件下将细菌加载到呼吸器过滤器上：无营养；存在人类唾液（模拟佩戴呼吸器时的情况）；存在营养肉汤（用于理想生长潜力）。后续实验模拟在中等工作负荷条件下以56升/分钟的呼吸频率佩戴呼吸器2小时。
发现耻垢分枝杆菌在测试的呼吸器上没有生长，即使呼吸器在最有利于微生物生长的温度、湿度和营养条件下储存。然而，这些细菌在储存期间可在呼吸器上存活长达3天。耻垢分枝杆菌的可培养性不受模拟中等工作负荷条件下2小时呼吸频率的气流影响。
本研究表明，在呼吸器上收集的结核分枝杆菌替代菌无法生长，并且仅在理想条件下（即与临床无关的条件）才能存活。基于这些实验，我们得出结论，一旦结核分枝杆菌被呼吸器去除，它不太可能再次在空气中成为感染问题。
