产牛乳球菌是美国重要的新兴水产养殖病原体。为了更好地了解有利于猪乳球菌病的环境条件和鱼类的易感性,实验室控制的挑战被用作感染模型.维持在13或18°C的虹鳟鱼Oncorhynchusmykiss通过每条鱼(CFU鱼-1)101、103或105个菌落形成单位的细胞内(ICe)注射攻击,并监测21天。在13°C,鳟鱼经历了7%、7%和0%的死亡率,幸存者的细菌持久性为0%,20%和0%,分别。当暴露于相同的细菌剂量时,保持在18°C的鳟鱼死亡率分别为59%,84%和91%,幸存者中细菌的持久性为60%,66%和0%,证实温度在乳球菌病的发病机理中的重要作用。此外,虹鳟鱼的易感性,奇努克鲑鱼Oncorhynchustshawytscha,白色st鱼Acipensertranmontanus,尼罗罗非鱼,在18°C下使用ICe挑战比较了鲤鱼对petauri感染的影响。鳟鱼和鲑鱼经历了96%和56%的累积死亡率,分别,而17%的存活鲑鱼仍然持续感染。其他鱼类没有死亡率,在攻击结束时没有可培养的细菌恢复。然而,当幸存的鱼被用于进一步的同居试验时,与先前暴露的罗非鱼一起饲养的幼稚鳟鱼表现出6%的死亡率,证明非沙门氏菌可以成为这种病原体的亚临床携带者。获得的数据提供了有关温度相关毒力的有用信息,鱼类物种易感性,和petauri的潜在载体传播,可用于开发更好的管理措施,以防止猪乳球菌病。
Lactococcus petauri is an important emergent aquaculture pathogen in the USA. To better understand environmental conditions conducive to piscine
lactococcosis and the susceptibility of fish species, laboratory-controlled challenges were used as models of infection. Rainbow trout Oncorhynchus mykiss maintained at 13 or 18°C were challenged by intracoelomic (ICe) injection with 101, 103 or 105 colony-forming units per fish (CFU fish-1) and monitored for 21 d. At 13°C, trout experienced mortalities of 7, 7 and 0%, and bacterial persistence of 0, 20 and 0% in survivors, respectively. When exposed to the same bacterial doses, trout maintained at 18°C experienced mortalities of 59, 84 and 91%, and bacterial persistence of 60, 66 and 0% in survivors, confirming a significant role of temperature in the pathogenesis of
lactococcosis. Additionally, the susceptibility of rainbow trout, Chinook salmon Oncorhynchus tshawytscha, white sturgeon Acipenser transmontanus, Nile tilapia Oreochromis niloticus, and koi Cyprinus carpio to infection by L. petauri was compared using ICe challenges at 18°C. Trout and salmon experienced 96 and 56% cumulative mortality, respectively, and 17% of surviving salmon remained persistently infected. There were no mortalities in the other fish species, and no culturable bacteria recovered at the end of the challenge. However, when surviving fish were used in further cohabitation trials, naïve trout housed with previously exposed tilapia exhibited 6% mortality, demonstrating that non-salmonids can become sub-clinical carriers of this pathogen. The data obtained provide useful information regarding temperature-associated virulence, fish species susceptibility, and potential carrier transmission of L. petauri that can be used in the development of better management practices to protect against piscine
lactococcosis.