Traditionally, fab cons are made from cationic surfactants and fragrance. The cationic surfactants consist of positively charged molecules while majority of bacteria have a net negative charge.
In effect, the fabric conditioner neutralizes the bacteria and kills them in the process making it inherently germicidal or antibacterial.
Make sure to choose a fabric conditioner that does not contain silicone. Silicone is another ingredient that does soften fabrics but is not antibacterial.