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

This study was conducted to determine a disease outbreak in ۱۴ day old post-larvae of abalone (Haliotis diversicolor supertexta) which caused mass mortality in July ۲۰۱۰ in Shanwei, China. Twenty-nine bacterial strains were isolated from a sample pool of ۱۰ diseased post-larval abalones on ۲۲۱۶E marine agar plates during a natural outbreak of the disease. Among them, a dominant isolate (referred to as strain ۲۱) was found to be highly virulent to post-larvae in experimental challenge tests, with an LD۵۰ value of ۱.۰ ×۱۰۴ colony forming units (CFU) mL-۱ on day ۳. API ۲۰NE kits and ۱۶S rDNA sequence analysis, identified strain ۲۱ as Oceanomonas doudoroffii. It was susceptible to ۱۰ and moderately susceptible to ۱ of the ۱۶ antibiotics examined when antibiotic sensitivities of the bacterium were assayed. Results of this study implicated Oceanomonas doudoroffii strain ۲۱ as a cause of mortalities in post-larval abalone from Shanwei, China.

Keywords:

Haliotis diversicolor supertexta , massive death , challenge test , Oceanomonas doudoroffii , ۱۶S rDNA sequencing