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Egg‐yolk trypticase soy agar for the enumeration of heat‐damaged spores of Clostridium sporogenes
Author(s) -
Michels M.J.M.,
Kagei R.F.
Publication year - 1983
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1983.tb01316.x
Subject(s) - spore , agar , yolk , food science , microbiology and biotechnology , clostridium sporogenes , agar plate , chemistry , biology , bacteria , clostridium , genetics
In heat‐resistance studies with spores of Clostridium sporogenes BC‐2, an improved recovery medium was needed for severely heat‐damaged spores as that used previously—Wynne medium in Miller‐Prickett tubes—did not allow accurate counts of spores because of gas formation and disruption of agar. Initial tests with pour plates of Viande‐Levure medium containing egg‐yolk gave much increased counts for spores previously heated for 50 min at 112°C; this increase was attributed to the presence of egg‐yolk. Addition of egg‐yolk to Reinforced Clostridial Agar, All‐Culture Medium and Trypticase Soy Agar showed that Trypticase Soy Agar with egg‐yolk was the best recovery medium. For the final formulation, the value of supplementation with cysteine‐HCl and methylene blue was also shown. The resultant Egg‐yolk Trypticase Soy Agar is conveniently prepared from BBL Trypticase Soy Agar (40 g) with the addition of 0.4 g/l cysteine‐HCl, 4 mg/1 of methylene blue and 2% Oxoid egg‐yolk emulsion aseptically to the melted basal medium. For optimal spore counts, pour plates are incubated anaerobically for 5–7 d at 30°C.