Watson Tifani R, Bruce Timothy J, Ma Jie, Cain Kenneth D
Department of Fish and Wildlife Sciences, College of Natural Resources, University of Idaho, Moscow, Idaho, 83844, USA.
Division of Aquaculture, Kentucky State University, Frankfort, Kentucky, 40601, USA.
J Aquat Anim Health. 2023 Mar;35(1):34-40. doi: 10.1002/aah.10175. Epub 2023 Mar 13.
Renibacterium salmoninarum is a pathogenic gram-positive bacterium and is the causative agent of bacterial kidney disease (BKD), a malady that mainly impacts salmonid species. Experimental challenges were conducted to assess the virulence and challenge route for select R. salmoninarum strains (CK-90 and ATCC 33739) in Rainbow Trout Oncorhynchus mykiss.
The CK-90 strain was intracoelomically injected (100 μL) at a high dose containing 4.80 × 10 CFU/g of fish (optical density at 525 nm [OD ] = 1.779) and a low dose containing 6.86 × 10 CFU/g of fish (OD = 1.077); alternatively, fish were immersed in a solution containing 4.5 × 10 CFU/mL of fish (OD = 0.886). The ATCC 33739 strain (originating from Brook Trout Salvelinus fontinalis) was also included and intracoelomically injected at 3.58 × 10 CFU/g of fish (OD = 1.431) to discern differences in virulence between the strains.
Clinical signs of BKD manifested at approximately 10 d postchallenge, and mortalities began at 19 days postchallenge. To confirm infection and quantify R. salmoninarum antigen load, an enzyme-linked immunosorbent assay (ELISA) was conducted using kidney tissue collected after the challenge. Rainbow Trout that were challenged with CK-90 by injection (both high- and low-dose groups) exhibited significantly higher mortality than fish that were injected with ATCC 33739 or those that were exposed to CK-90 via immersion challenge. The R. salmoninarum p57 (57-kDa protein) antigen was confirmed via ELISA. Antigen load for fish injected with CK-90 (high dose: OD = 0.71; low dose: OD = 0.66) was significantly higher than that for fish injected with ATCC 33739 (OD = 0.34). The CK-90 strain (both high and low doses) was more virulent than ATCC 33739, which caused no mortalities over the 28-days trial. Although there were no mortalities among ATCC 33739 fish, the ELISA confirmed that the R. salmoninarum antigen infiltrated kidney tissue in those fish.
The immersion challenge methodology for R. salmoninarum CK-90 was ineffective for inducing mortalities at the examined dose.
鲑肾杆菌是一种致病性革兰氏阳性菌，是细菌性肾病（BKD）的病原体，这种疾病主要影响鲑科鱼类。进行了实验性攻毒试验，以评估选定的鲑肾杆菌菌株（CK - 90和ATCC 33739）对虹鳟Oncorhynchus mykiss的毒力和攻毒途径。
以高剂量（每克鱼含4.80×10 CFU，525 nm处光密度[OD ] = 1.779）和低剂量（每克鱼含6.86×10 CFU，OD = 1.077）腹腔注射（100 μL）CK - 90菌株；或者，将鱼浸入含有每毫升鱼4.5×10 CFU（OD = 0.886）的溶液中。还纳入了ATCC 33739菌株（源自溪红点鲑Salvelinus fontinalis），以每克鱼3.58×10 CFU（OD = 1.431）的剂量腹腔注射，以辨别菌株间毒力的差异。
攻毒后约10天出现BKD的临床症状，攻毒后19天开始出现死亡。为确认感染并量化鲑肾杆菌抗原载量，使用攻毒后收集的肾脏组织进行了酶联免疫吸附测定（ELISA）。通过注射（高剂量和低剂量组）用CK - 90攻毒的虹鳟的死亡率显著高于注射ATCC 33739的鱼或通过浸浴攻毒接触CK - 90的鱼。通过ELISA确认了鲑肾杆菌p57（57 kDa蛋白）抗原。注射CK - 90的鱼（高剂量：OD = 0.71；低剂量：OD = 0.66）的抗原载量显著高于注射ATCC 33739的鱼（OD = 0.34）。CK - 90菌株（高剂量和低剂量）比ATCC 33739毒力更强，在28天的试验中ATCC 33739未导致死亡。尽管ATCC 33739组的鱼没有死亡，但ELISA证实该组鱼的肾脏组织中有鲑肾杆菌抗原浸润。
在所检测的剂量下，鲑肾杆菌CK - 90的浸浴攻毒方法诱导死亡无效。
