McMullin Bevin B, Chittock Dean R, Roscoe Diane L, Garcha Harjinder, Wang Lexin, Miller Christopher C
Respiratory Services, Vancouver Coastal Health at University of British Columbia, Vancouver, British Columbia, Canada.
Respir Care. 2005 Nov;50(11):1451-6.
Nosocomial pneumonia is the second most frequent nosocomial infection and the leading cause of death from hospital-acquired infection. Endogenously produced nitric oxide is an important component of the body's natural defense mechanism. Recent studies have demonstrated that exogenous gaseous nitric oxide (gNO) is bactericidal and that inhaled gNO is beneficial to bacterial clearance.
Determine the antimicrobial effect of exogenous gNO in vitro against organisms from culture collections and pathogens derived from tracheal aspirates of mechanically ventilated patients with pneumonia in an intensive care unit.
Using bacterial isolates in pure culture, a 0.5 McFarland standard (10(8) colony-forming-units [cfu] per mL) was prepared and further diluted to 1:1,000 with saline, to 10(5) cfu/mL. For each isolate tested, 3 mL was pipetted into each well of a 6-well plate, and placed in a specially designed incubator with compartments for both a treatment arm and a control arm. Both chambers received a continuous flow of heated, humidified gas. The treatment chamber had 200 ppm of gNO in the gas flow, which is higher than the clinically accepted concentration for gNO. Samples were drawn off at time intervals, plated onto Columbia agar base with 5% sheep blood, and placed in a traditional incubator at 35 degrees C for a minimum of 24 h. All tests were performed in duplicate. The colony-forming units were visually counted to determine percentage kill.
There was total kill (100% of all colony-forming units) of each bacterial strain subjected to the test conditions at between 2 and 6 h of exposure to 200 ppm gNO.
gNO is bactericidal against various strains of bacteria suspended in saline, including both Gram-positive and Gram-negative organisms, and those that commonly cause nosocomial pneumonia in mechanically ventilated patients. Future work should focus on developing strategies that maximize the antimicrobial effect while minimizing the effect of these same interventions on host cells.
医院获得性肺炎是第二常见的医院感染类型，也是医院获得性感染致死的主要原因。内源性产生的一氧化氮是机体自然防御机制的重要组成部分。近期研究表明，外源性气态一氧化氮（gNO）具有杀菌作用，吸入gNO有利于细菌清除。
确定外源性gNO在体外对来自菌种保藏机构的菌株以及重症监护病房中机械通气肺炎患者气管吸出物中分离出的病原体的抗菌效果。
使用纯培养的细菌分离株，制备0.5麦氏标准液（每毫升10⁸菌落形成单位[cfu]），并用生理盐水进一步稀释至1:1000，即10⁵ cfu/mL。对于每个测试的分离株，吸取3 mL加入6孔板的每个孔中，并置于专门设计的培养箱中，该培养箱有用于处理组和对照组的隔层。两个腔室均接受加热、加湿的气体持续流通。处理腔室的气流中有200 ppm的gNO，这高于gNO的临床公认浓度。每隔一定时间取样，接种到含5%羊血的哥伦比亚琼脂基础培养基上，置于35℃的传统培养箱中至少培养24小时。所有测试均重复进行。通过肉眼计数菌落形成单位以确定杀菌率。
在暴露于200 ppm gNO的2至6小时内，每种受试细菌菌株的所有菌落形成单位均全部被杀灭（100%）。
gNO对悬浮于盐水中的各种细菌菌株具有杀菌作用，包括革兰氏阳性菌和革兰氏阴性菌，以及那些在机械通气患者中常见的引起医院获得性肺炎的细菌。未来的工作应集中于制定策略，在使抗菌效果最大化的同时，尽量减少这些干预措施对宿主细胞的影响。
