CASP9 and bacterial infectious disease: Following the initial quantification of apoptotic gene expression in bacterial infections, subsequent analyses focused on aif and caspase 3/8/9, as these molecules represent functionally distinct yet interconnected nodes of the apoptotic machinery: AIF mediates caspase-independent intrinsic apoptosis, while caspase 3 (effector), caspase 8 (extrinsic pathway initiator), and caspase 9 (intrinsic pathway initiator) collectively orchestrate caspase-dependent apoptotic signaling.