Interactions between Clostridium perfringens spores and Raw 264.7 macrophages.

Clostridium perfringens is the causative agent of a variety of histotoxic infections in humans and animals. Studies on the early events of C. perfringens infections have been largely focused on the interactions between their vegetative cells and macrophages. Consequently, in the current study we have examined the interactions between C. perfringens spores and Raw 264.7 macrophages. Raw 264.7 cells were able to interact and phagocytose Clostridium perfringens spores of a food poisoning isolate, strain SM101, and a non-food borne isolate, strain F4969, albeit to different extents. Phagocytosis and to a lesser extent, association, of C. perfringens spores by Raw 2647 macrophages was completely inhibited in presence of cytochalasin D. Complement increased association and phagocytosis of C. perfringens spores by Raw 264.7 macrophages. Survival of C. perfringens spores during macrophage infection seems to depend on the ability of spore germination during infection as: (i) F4969 spores germinated during infection with Raw 264.7 macrophages and subsequently killed by macrophages; and (ii) SM101 spores remained dormant inside Raw 264.7 macrophages and thus survived up to 24 h of infection. The in vitro spore-resistance factors, α/β-type SASP, SpmA/B proteins and spore's core water content, seems to play no role in mediating SM101 spore-resistance to macrophages. Collectively, these results might well have implications in understanding the initial stages of infections by C. perfringens spores.