Ford Susan E, Chintala Marnita M, Bushek David
Haskin Shellfish Research Laboratory, Institute of Marine and Coastal Sciences, Rutgers University, 6959 Miller Avenue, Port Norris, New Jersey 08349, USA.
Dis Aquat Organ. 2002 Oct 4;51(3):187-201. doi: 10.3354/dao051187.
Perkinsus marinus is a highly contagious pathogen of the eastern oyster Crassostrea virginica. Until recently, transmission studies have employed wild-type parasites isolated directly from infected oysters. Newly developed methods to propagate P. marinus in vitro have led to using cultured parasites for infection studies, but results suggest that cultured parasites are less virulent than wild-type parasites In this paper, we report results of experiments designed to quantify differences between wild-type and cultured P. marinus virulence and to test the following hypotheses: (1) in vitro-cultured parasites are less virulent than wild-type parasites; (2) virulence decreases gradually during in vitro culture; (3) virulence of in vitro cultures can be restored by in vivo passage; (4) virulence changes with culture phase. Our results demonstrate that parasites freshly isolated from infected hosts are much more virulent than those propagated in culture, indicating a potential deficiency in the culture medium used. Virulence was lost immediately in culture and, for that reason, the practice of repassing cultured cells through the host to restore virulence does not work for P. marinus. Virulence was also associated with culture phase: log-phase parasites were significantly more virulent than those obtained from lag- or stationary-phase cultures.
海洋派金虫是美国东海岸牡蛎（Crassostrea virginica）的一种高传染性病原体。直到最近，传播研究一直使用直接从受感染牡蛎中分离出的野生型寄生虫。新开发的在体外繁殖海洋派金虫的方法使得在感染研究中开始使用培养的寄生虫，但结果表明，培养的寄生虫的毒性低于野生型寄生虫。在本文中，我们报告了旨在量化野生型和培养的海洋派金虫之间的毒力差异并检验以下假设的实验结果：（1）体外培养的寄生虫的毒性低于野生型寄生虫；（2）在体外培养过程中毒力逐渐降低；（3）体外培养物的毒力可通过体内传代恢复；（4）毒力随培养阶段而变化。我们的结果表明，从受感染宿主中新鲜分离出的寄生虫比在培养物中繁殖的寄生虫毒性大得多，这表明所用培养基可能存在缺陷。在培养过程中毒力立即丧失，因此，将培养的细胞通过宿主传代以恢复毒力的做法对海洋派金虫不起作用。毒力也与培养阶段有关：对数期的寄生虫比从延迟期或稳定期培养物中获得的寄生虫毒性明显更大。
