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ENUMERATION OF THERMALLY STRESSED Staphylococcus aureus MF 31
Author(s) -
GRAY RODNEY J. H.,
GASKE MARGARET A.,
ORDAL Z. JOHN
Publication year - 1974
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1974.tb17992.x
Subject(s) - enumeration , staphylococcus aureus , food science , microbiology and biotechnology , phosphate buffered saline , most probable number , chemically defined medium , potassium phosphate , chemistry , food microbiology , biology , bacteria , chromatography , biochemistry , in vitro , mathematics , genetics , combinatorics
Procedures used to enumerate microorganisms in food should detect all viable organisms present, regardless of their physiological state. Several currently recognized procedures were unable to satisfactorily enumerate thermally stressed cells of Staphylococcus aureus . After heating cells at 52°C in 100 mM potassium phosphate buffer pH 7.2, the cells were enumerated by comparative platings on both selective and nonselective media and by a most probable number technique (MPN). All media produced similar counts of unheated cells. When heated cells were enumerated by plating on selective media, productivity varied with the degree of stress imposed and the particular medium used. Baird‐Parker's medium enumerated normal and stressed cells equally well. When stressed cells were inoculated into trypticase soy broth + 10% NaCl the plate count on the nonselective medium decreased and approached that of the selective medium. After an extended lag the counts then increased in a parallel manner.