DELAYED-INCUBATION METHOD FOR MICROBIOLOGICAL ANALYSIS OF ENVIRONMENTAL SPECIMENS AND SAMPLES

Five laboratories compared the quantitative recovery of heterotrophic bacteria, yeasts and molds, coliforms, Escherichia coli, Pseudomonas a eruginosa, and Staphylococcus aureus from a variety of naturally conta minated food and water samples, using traditional incubation procedure s and a delayed-incubation method. Refrigeration of inoculated media f or up to 3 days prior to incubation was shown to be a viable option fo r many quantitative analyses, but needs to be validated for each appli cation. Some inoculated media withstood refrigeration for up to 7 days prior to incubation without any detrimental effect on the recovery of target cells, while the incubation of other media for similar types o f analyses could not be delayed even for 3 days.