Clostridium perfringens
The CDCs "Streptococcus pneumoniae" Pneumolysin, "Clostridium perfringens" perfringolysin O, and "Listeria monocytogenes" listeriolysin O cause specific modifications of histones in the host cell nucleus, resulting in down-regulation of several genes that encode proteins involved in the inflammatory response. Histone modification does not involve the pore-forming activity of the CDCs.