A leukocidin is a type of cytotoxin created by some types of bacteria (Staphylococcus). It is a type of pore-forming toxin. Leukocidins get their names by killing ("-cide") leukocytes. Leukocidins fall into the category of bacterial invasin. Invasins are enzymatic secretions that help bacteria invade the host tissue to which they are attached. Although similar to exotoxins, invasins are different in two respects: they work through much less specific mechanisms than exotoxins, and their actions are generally more localized.
One type is Panton-Valentine leukocidin.