Comparison of four routine methods for the confirmation of Clostridium perfringens in food

In order to compare methods for the confirmation of C. perfringens 52 isola tes from strain collections and food samples were examined using four diffe rent techniques including the detection of lactose degradation and sulfite reduction in lactose sulfite medium (European Standard EN 13401), examinati on of nitrate reduction, motility, lactose degradation and gelatine liquefa ction in motility-nitrate and lactose-gelatine medium (EN 13401), the rever se CAMP test (German Standard DIN 10103) and the acid phosphatase reaction according to Ueno et at. [Ueno, K., Fujii, H., Marui, T., Takahshi, J., Sug itani, T., Ushijima, T., Suzuki, S. 1970. Acid phosphatase in Clostridium p erfringens - A new rapid and simple identification method. Jpn. J. Microbio l. 14, 171-173]. Pure cultures of the test strains were suspended in steril e physiological saline and decimal dilutions inoculated into modified SC ag ar according to Hauschild and Hilsheimer [Hauschild, A.H.W., Hilsheimer, R. , 1974. Evaluation and modifications of media for enumeration of Clostridiu m perfringens. Appl. Microbiol. 27, 521-526] and Eisgruber and Reuter [Eisg ruber, H., Reuter, G., 1995. A selective medium for the detection and enume ration of mesophilic sulphite-reducing clostridia in food monitoring progra ms. Food Res. Internat. 28, 219-226] by pour-plating. Five individual colon ies per test strain (in total 260 colonies) were examined. Using either the reverse CAMP test or the acid phosphatase reaction 94.2% of the colonies w ere confirmed as C. perfringens. The detection of nitratase and motility in combination with lactose and gelatine degradation enabled the identificati on of C. perfringens in 88.5% of the colonies. The lowest percentage of C. perfringens colonies was detected via lactose sulfite medium: only 42.7% of the tested colonies showed typical sulfite reduction with gas formation fr om lactose. (C) 2000 Elsevier Science B.V. All rights reserved.