Dong H T, Senapin S, LaFrentz B, Rodkhum C
Department of Veterinary Microbiology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok, Thailand.
National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Pathumthani, Thailand.
J Fish Dis. 2016 Jun;39(6):649-55. doi: 10.1111/jfd.12385. Epub 2015 May 7.
Numerous isolates of Flavobacterium columnare were previously recovered from red tilapia, Oreochromis sp., exhibiting columnaris-like disease in Thai farms, and the phenotypic and genetic characteristics were described. The objective of this study was to determine the virulence of two morphotypes (rhizoid and non-rhizoid colonies) of F. columnare and to determine their ability to adhere to and persist in red tilapia fry. The results showed that the typical rhizoid isolate (CUVET1214) was a highly virulent isolate and caused 100% mortality within 24 h following bath challenge of red tilapia with three different doses. The non-rhizoid isolate (CUVET1201) was avirulent to red tilapia fry. Both morphotypes adhered to and persisted in tilapia similarly at 0.5 and 6 h post-challenge as determined by whole fish bacterial loads. At 24 and 48 h post-challenge, fry challenged with the rhizoid morphotype exhibited significantly higher bacterial loads than the non-rhizoid morphotype. The results suggested that an inability of the non-rhizoid morphotype to persist in tilapia fry may explain lack of virulence.
此前，从泰国养殖场患有柱状样疾病的红罗非鱼（Oreochromis sp.）中分离出了大量柱状黄杆菌菌株，并对其表型和遗传特征进行了描述。本研究的目的是确定柱状黄杆菌两种形态型（根状和非根状菌落）的毒力，并确定它们在红罗非鱼苗中黏附及持续存在的能力。结果表明，典型的根状分离株（CUVET1214）是一种高毒力分离株，在用三种不同剂量对红罗非鱼进行浸浴攻毒后24小时内导致100%的死亡率。非根状分离株（CUVET1201）对红罗非鱼苗无毒力。通过全鱼细菌载量测定，在攻毒后0.5小时和6小时，两种形态型在罗非鱼体内的黏附及持续存在情况相似。在攻毒后24小时和48小时，用根状形态型攻毒的鱼苗体内细菌载量显著高于非根状形态型。结果表明，非根状形态型无法在罗非鱼苗体内持续存在可能解释了其无毒力的原因。
