Isolation, identification and phylogenetic analysis of a pathogen of Haliotis diversicolor supertexta (L.) with mass mortalities

Studies were conducted to determine a disease outbreak in 14 day old post-larvae of abalone (haliotis diversicolor supertexta) which caused mass mortality in july 2010 in shanwei, china. twenty-nine bacterial strains were isolated from a sample pool of 10 diseased post-larval abalones on 2216e marine agar plates during a natural outbreak of the disease. among them, a dominant isolate (referred to as strain 21) was found to be highly virulent to post-larvae in experimental challenge tests, with an ld50 value of 1.0 ×104 colony forming units (cfu) ml-1 on day 3. api 20ne kits and 16s rdna sequence analysis, identified strain 21 as oceanomonas doudoroffii. it was susceptible to 10 and moderately susceptible to 1 of the 16 antibiotics examined when antibiotic sensitivities of the bacterium were assayed. results of this study implicated oceanomonas doudoroffii strain 21 as a cause of mortalities in post-larval abalone from shanwei, china.