On blood agar target appearance of Cl. perfringens is due to which toxin ?
Ans. is 'a' i.e., Alpha toxin Two impoant characteristic feature of Cl. perfringens are :?Target hemolysis (double zone hemolysis) on blood agar. It is a narrow zone of complete hemolysis by theta toxin which is surrounded by a wider incomplete hemolysis by alpha-toxin.Naegler's reaction detects alpha toxin (phospholipase or lecithinase C). When Cl. perfringens is grown on a medium with the antitoxin spread on one half of the plate, colonies on the other half without the antitoxin will be surrounded by a zone of opacity. There will be no opacity around the colonies on the half of the plate with the antitoxin, due to the specific neutralisation of the alpha-toxin.
Alpha toxin
Theta toxin
Beta toxin
Mu toxin