Dobrowsky Penelope H, Khan Sehaam, Khan Wesaal
Department of Microbiology, Faculty of Science, Stellenbosch University, Private Bag X1, Stellenbosch 7602, South Africa.
Faculty of Health and Applied Sciences, Namibia University of Science and Technology,13 Storch Street, Private Bag 13388, Windhoek, Namibia.
Environ Res. 2017 Oct;158:82-93. doi: 10.1016/j.envres.2017.06.003. Epub 2017 Jun 10.
Legionella and Acanthamoeba spp. persist in harvested rainwater pasteurized at high temperatures (> 72°C) and the interaction mechanisms exhibited between these organisms need to be elucidated. The resistance of two Legionella reference strains (Legionella pneumophila ATCC 33152 and Legionella longbeachae ATCC 33462), three environmental strains [Legionella longbeachae (env.), Legionella norrlandica (env.) and Legionella rowbothamii (env.)] and Acanthamoeba mauritaniensis ATCC 50676 to heat treatment (50-90°C) was determined by monitoring culturability and viability [ethidium monoazide quantitative polymerase chain reaction (EMA-qPCR)]. The expression of metabolic and virulence genes of L. pneumophila ATCC 33152 (lolA, sidF, csrA) and L. longbeachae (env.) (lolA) in co-culture with A. mauritaniensis ATCC 50676 during heat treatment (50-90°C) was monitored using relative qPCR. While the culturability (CFU/mL) and viability (gene copies/mL) of the Legionella strains reduced significantly (p < 0.05) following heat treatment (60-90°C), L. longbeachae (env.) and L. pneumophila ATCC 33152 were culturable following heat treatment at 50-60°C. Metabolically active trophozoites and dormant cysts of A. mauritaniensis ATCC 50676 were detected at 50°C and 60-90°C, respectively. For L. pneumophila ATCC 33152, lolA expression remained constant, sidF expression increased and the expression of csrA decreased during co-culture with A. mauritaniensis ATCC 50676. For L. longbeachae (env.), while lolA was up-regulated at 50-70°C, expression was not detected at 80-90°C and in co-culture. In conclusion, while heat treatment may reduce the number of viable Legionella spp. in monoculture, results indicate that the presence of A. mauritaniensis increases the virulence of L. pneumophila during heat treatment. The virulence of Legionella spp. in co-culture with Acanthamoeba spp. should thus be monitored in water distribution systems where temperature (heat) is utilized for treatment.
嗜肺军团菌和棘阿米巴属在高温（>72°C）巴氏消毒的收集雨水中持续存在，这些生物体之间表现出的相互作用机制需要阐明。通过监测可培养性和活力[单叠氮乙锭定量聚合酶链反应（EMA-qPCR）]，测定了两株嗜肺军团菌参考菌株（嗜肺军团菌ATCC 33152和长滩军团菌ATCC 33462）、三株环境菌株[长滩军团菌（环境株）、诺尔兰军团菌（环境株）和罗伯塔姆军团菌（环境株）]以及毛里塔尼亚棘阿米巴ATCC 50676对热处理（50-90°C）的抗性。使用相对定量PCR监测了嗜肺军团菌ATCC 33152（lolA、sidF、csrA）和长滩军团菌（环境株）（lolA）在与毛里塔尼亚棘阿米巴ATCC 50676共培养期间热处理（50-90°C）时代谢和毒力基因的表达。虽然嗜肺军团菌菌株在热处理（60-90°C）后可培养性（CFU/mL）和活力（基因拷贝数/mL）显著降低（p<0.05），但长滩军团菌（环境株）和嗜肺军团菌ATCC 33152在50-60°C热处理后仍可培养。分别在50°C和60-90°C检测到毛里塔尼亚棘阿米巴ATCC 50676的代谢活跃滋养体和休眠包囊。对于嗜肺军团菌ATCC 33152，在与毛里塔尼亚棘阿米巴ATCC 50676共培养期间，lolA表达保持恒定，sidF表达增加，csrA表达降低。对于长滩军团菌（环境株），虽然lolA在50-70°C上调，但在80-90°C及共培养时未检测到表达。总之，虽然热处理可能会减少纯培养中嗜肺军团菌属的活菌数量，但结果表明毛里塔尼亚棘阿米巴的存在会增加嗜肺军团菌在热处理期间的毒力。因此，在利用温度（加热）进行处理的供水系统中，应监测嗜肺军团菌属与棘阿米巴属共培养时其毒力情况。
