COMPARISON OF EGG‐YOLK‐FREE TRYPTOSE SULFITE CYCLOSERINE AND SHAHIDI‐FERGUSON‐PERFRINGENS MEDIA FOR ENUMERATION OF CLOSTRIDIUM PERFRINGENS IN MEAT PRODUCTS AND PEPTONE WATER USING FUNG'S DOUBLE TUBE METHOD1

Abstract

This study compared the ability of Clostridium perfringens to recover in Fung's Double Tube (FDT) system using either tryptose‐sulfite‐cycloserine without egg yolk (TSC) or Shahidi‐Ferguson‐perfringens (SFP) agar both in three typical meat products and peptone water. A three‐strain cocktail of C. perfringens spores (ATCC 10388, NCTC 8238, and NCTC 8239) was inoculated in each food system at three inoculum levels: 102, 104, and 106 cfu/g or mL. FDT system consists of a smaller glass test tube inserted into a larger glass test tube in which sample and agar have been poured. By inserting the inner tube, the agar squeezes between the exterior wall of the small tube and the interior wall of the larger tube to form a thin agar layer, which creates an anaerobic environment. Tubes are then incubated in aerobic incubators. There were no significant differences in enumeration of C. perfringens between the two media in any of the meat products and peptone water at any inoculation level. Thus, the use of SFP, which is less expensive and easier to prepare than TSC, is recommended as an alternative agar for analyses of C. perfringens in FDT system. Compared to the petri dish method, the FDT method generates greater anaerobiosis, is easier to prepare, more compact, and eliminates the need for an overlay and an anerobic chamber or jar. Combined together, the use of SFP in the FDT system provides an efficient, easy‐to‐use method that is less expensive than the conventional method to detect and enumerate C. perfringens in foods.