Identification and Biological Characteristics of the Pathogen Causing Macrobrachium nipponense Soft-shell Syndrome

Abstract:

A pathogenic bacterial strain QXL0711B was isolated from freshwater shrimp (Macrobrachium nipponense) suffering with soft-shell syndrome. The 50% lethal concentration (LC50) of strain QXL0711B was 1.47×106 CFU/mL, which showed that strain QXL0711B was rather strong virulent to Macrobrachium nipponense. Strain QXL0711B was gram negative and had β-hemolytic activity on sheep blood agar. By means of API 32E identification and 16S rRNA sequence analysis, strain QXL0711B was identified as Aeromonas veronii biovar sobria (locus number: FJ808727), which was the closest relative to Aeromonas veronii strain (locus number: X71120) and Aeromonas veronii biovar sobria strain (locus number: AY987729) with 99% homology. In addition, strain QXL0711B was highly sensitive to ceftriaxone ceftazidime ciprofloxacin enrofloxacin and norfloxacin.