Rapid Detection of Excessive CFU Counts of Enterobacteriaceae, S. aureus and Yeasts by Nitrate Reduction/Glucose Dissimilation (NGD) Monitoring in Selective Media

摘要

ABSTRACTA technique was developed for the approximate selective estimation of CFU loads of thermotrophic Enterobacteriaceae and S.aureusin foods and meals, relying on rate of nitrate reduction and glucose dissimilation (NGD test) in lauryl sulfate nitrate glucose broth and modified liquid Baird Parker medium with nitrate and glucose added, respectively, both incubated at 42.5°C. Yeast CFU could be assessed similarly in oxytetracyclin gentamicin glucose broth at 30°C. The fate of nitrate and glucose was monitored by urinanalysis dip sticks. Response times were 7 and 2 hr for CFU levels of 105and 108g−1, respectively, allowing feedback to production lines within one working day. The procedure requiring no other instrumentation than a centrifuge, also has been applied successfully as a field test proced