<i>Nocardia seriolae</i> and <i>Streptococcus iniae</i> Co‐Infection in Cultured Fourfinger threadfin, <i>Eleutheronema tetradactylum</i> , in Singapore

ABSTRACT Between April and May 2021, two batches of diseased fourfinger threadfin ( Eleutheronema tetradactylum ) from an open‐sea net cage farm were submitted for diagnostic post‐mortem examination. Necropsy and histopathology identified necrosis within multiple organs with intralesional Gram‐positive, branching, beaded filamentous bacilli suggestive of Nocardia species. Intralesional Gram‐positive cocci were also observed within the heart sections. These Gram‐positive bacilli and cocci were subsequently confirmed to be Nocardia seriolae and Streptococcus iniae , respectively, through isolation, PCR and sequencing. This is the first report from Singapore of N. seriolae and S. iniae co‐infection and outbreak in cultured fourfinger threadfin.