Diaz S Anaid, Restif Olivier
Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
Disease Dynamics Unit, Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.
Appl Environ Microbiol. 2014 Sep;80(17):5411-8. doi: 10.1128/AEM.01037-14. Epub 2014 Jun 27.
Caenorhabditis elegans is frequently used as a model species for the study of bacterial virulence and innate immunity. In recent years, diverse mechanisms contributing to the nematode's immune response to bacterial infection have been discovered. Yet despite growing interest in the biochemical and molecular basis of nematode-bacterium associations, many questions remain about their ecology. Although recent studies have demonstrated that free-living nematodes could act as vectors of opportunistic pathogens in soil, the extent to which worms may contribute to the persistence and spread of these bacteria has not been quantified. We conducted a series of experiments to test whether colonization of and transmission between C. elegans nematodes could enable two opportunistic pathogens (Salmonella enterica and Pseudomonas aeruginosa) to spread on agar plates occupied by Escherichia coli. We monitored the transmission of S. enterica and P. aeruginosa from single infected nematodes to their progeny and measured bacterial loads both within worms and on the plates. In particular, we analyzed three factors affecting the dynamics of bacteria: (i) initial source of the bacteria, (ii) bacterial species, and (iii) feeding behavior of the host. Results demonstrate that worms increased the spread of bacteria through shedding and transmission. Furthermore, we found that despite P. aeruginosa's relatively high transmission rate among worms, its pathogenic effects reduced the overall number of worms colonized. This study opens new avenues to understand the role of nematodes in the epidemiology and evolution of pathogenic bacteria in the environment.
秀丽隐杆线虫经常被用作研究细菌毒力和先天免疫的模式物种。近年来，人们发现了多种导致线虫对细菌感染产生免疫反应的机制。然而，尽管对线虫与细菌关联的生化和分子基础的兴趣日益浓厚，但关于它们的生态学仍有许多问题。尽管最近的研究表明，自由生活的线虫可能在土壤中充当机会性病原体的载体，但线虫对这些细菌的持续存在和传播的贡献程度尚未得到量化。我们进行了一系列实验，以测试秀丽隐杆线虫的定殖和传播是否能使两种机会性病原体（肠炎沙门氏菌和铜绿假单胞菌）在被大肠杆菌占据的琼脂平板上传播。我们监测了肠炎沙门氏菌和铜绿假单胞菌从单个受感染线虫到其后代的传播情况，并测量了线虫体内和平板上的细菌载量。特别是，我们分析了影响细菌动态的三个因素：（i）细菌的初始来源，（ii）细菌种类，以及（iii）宿主的摄食行为。结果表明，线虫通过脱落和传播增加了细菌的传播。此外，我们发现，尽管铜绿假单胞菌在蠕虫中的传播率相对较高，但其致病作用减少了定殖蠕虫的总数。这项研究为理解线虫在环境中病原菌的流行病学和进化中的作用开辟了新途径。
