Chapter 32 - Nocardiosis

Abstract

The Nocardia sp. bacterium has a rod, coccoid, or filamentous appearance, with bead-like acid-fast staining. Nocardia sp. is the causative agent of nocardiosis, a lethal systemic granulomatous disease of the skin, muscle, and various inner tissues affecting various teleost. Three species of Nocardia have been isolated from diseased fish, namely Nocardia asteroides, Nocardia seriolae, and Nocardia salmonicida. Therefore, in fish aquaculture, nocardiosis has caused severe economic losses, especially in the Asian region, especially in Japan and Taiwan. Bacterial isolation from diseased fish showed growth on brain heart infusion agar, blood agar, and Löwenstein–Jensen agar at three days when incubated at 25°C. The polymerase chain reaction (PCR) assay with primers NS1 and NG1 based on unique regions of the N. seriolae 16S rRNA gene allows for its specific identification and yields the 432-bp amplicon. To distinguish among the Nocardia sp., phylogenetic analyses are available, based on the sequences of heat shock protein gene, RNA polymerase gene B, and 16S rRNA. Transcriptome analysis may provide a valuable insight for further research in immune response and strategies against N. seriolae infection in teleost fishes. The subunit vaccines are promising vaccine candidates for preventing N. seriolae disease in largemouth bass. The pAg85Lwt and pAg85Lopt DNA vaccine may confer protective efficacy against N. seriolae infection in amberjack.