English

Wang Pei-Chi,Chen Shih-Chu,Chan Yanting,Tsai Ming-An,Liang Yu-Chi

doi:10.5897/ajmr2014.6874

Abstract

A Nocardia seriolae was isolated from diseased spotted butterfish (Scatophagus argus, Linn). The cumu-lative mortality within one month was 30% (660 out of 2200). The diseased fish were two years old with lengths from 18 to 25 cm. Most fish suffered from haemorrhages and ulcers of the skin. The most significant gross pathological change was enlargement of the spleen, kidney and liver. White nodules, varying in size, were found in these organs. The isolated bacteria were either coccoid or filamentous in appearance, with bead-like staining. The identification of NS128 was verified by polymerase chain reaction (PCR) assay for N. seriolae that gave the expected specific amplicon of 432 bp of the 16S rDNA sequence with a 100% sequence identity with N. seriolae (GenBank accession number AF380937). A partial sequence of the 16S rRNA gene (GenBank accession number EU147501), the RNA polymerase B subunit (rpo B) gene (GenBank accession number DQ119300) and the heat shock protein gene (GenBank accession number DQ431437) of the organism, NS128 and the type strain of N. seriolae BCRC 13745 formed a monophyletic clade with a high sequence similarity and a bootstrap of 100%. White nodules that were induced in experimental fish, spotted butterfish and amberjack (Seriola dumerili, Risso) were similar to those in naturally infected fish cases and N. seriolae were re-isolated using brain heart infusion agar. These finding provides evidence that N. seriolae caused systemic granulomas in spotted butterfish. Based on the growth characteristics, and biochemical properties of the bacterium, its histopathological changes, PCR and the phylogenetic analysis, the pathogenic organism was identified as N. seriolae. This investigation is the first published on N. seriolae infection in spotted butterfish in aquaculture. The results reveal that the N. seriolae isolated in the field was pathogenic to spotted butterfish and amberjack. Key words: Pathogenicity, Nocardia seriolae, spotted butterfish, Scatophagus argus, polymerase chain reaction (PCR).

Highlights

Noca ardia seriolae s e, a ca ausativ ve agen nt of sy ystematic granuloma in spottted bu utterfis sh, Sca atopha agus arrgus, Linn
We describe the first isolation and characterization of pathogenic Nocardia species obtained from diseased spotted butterfish, Scatophagus argus with systematic granuloma during an outbreak of nocardiosis in the summer of 2005 in Taiwan
Spotted butterfish when infected with N. seriolae exhibit gross lesions and histopathological changes that are similar to those observed in three striped tigerfish (Wang et al, 2009)

Summary

Introduction

Noca ardia seriolae s e, a ca ausativ ve agen nt of sy ystematic granuloma in spottted bu utterfis sh, Sca atopha agus arrgus, Linn. We describe the first isolation and characterization of pathogenic Nocardia species obtained from diseased spotted butterfish, Scatophagus argus with systematic granuloma during an outbreak of nocardiosis in the summer of 2005 in Taiwan. The isolate from spotted butterfish was cultured and identified as N. seriolae using PCR methods.

Results

Conclusion