Production of gas and acid from lactose and liquefaction of gelatin
15. The presence of Clostridium perfringens shall be determined on the basis of the results from paragraphs 10 to 14. Bacteria which produce black colonies on SF agar, are non-motile, reduce nitrate to nitrite, produce gas and acid from lactose and liquefy gelatin within 48 hours shall be considered to be Clostridium perfringens.