Induction of apoptosis in tilapia, Oreochromis aureus Steindachner, and in TO-2 cells by Staphylococcus epidermidis

This study describes apoptosis induced in vivo and in vitro in tilapia, Oreochromis aureus Steindachner, by Staphylococcus epidermidis . In an in vivo experiment, tilapia were challenged using viable S. epidermidis and its cultured supernatant, respectively. Apoptosis was predominantly detected in lymphocytes and macrophages in spleen and kidney. Apoptotic figures were observed occasionally in the brain, liver, gonad, mesentery, stomach, intestine and skeletal muscle of infected fish. In an in vitro experiment, TO-2 cells treated with brain heart infusion broth supernatant of the bacteria after 48 h revealed that the supernatant was able to induce the cell apoptosis. Fragmented DNA was also detected 48 h after treatment using 1.5% agarose gel electrophoresis. The smallest multimeric DNA fragment was approximately 180-bp in length. Results of both the in vitro and in vivo experiments showed that products of the bacteria could induce tilapia cell apoptosis.