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Bacteriological stability of water bottled in plastic containers and the growth kinetics of Pseudomonas aeruginosa were determined. Samples of water from the source, water to be bottled, finished product and sterile water bottled in non‐returnable and returnable containers were analysed for aerobic colony count, coliforms, Escherichia coli and Ps. aeruginosa. The samples were examined for up to 30 d storage. Aerobic colony count increased 6 d after bottling to between 103 and 105 cfu ml−1. Coliforms and E. coli were not found in any sample. Pseudomonas aeruginosa was isolated from commercial products bottled in returnable plastic containers due to the contamination from the containers and the subsequent multiplication utilizing trace nutrients. The predominant Ps. aeruginosa strains showed high doubling time (26 h) due to competition from the accompanying flora. In the absence of competing flora Ps. aeruginosa reached higher density than the maximum reached by aerobic flora, with a doubling time of only 3·6 h. After 30 d storage, this micro‐organism was predominant.

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As a contribution to Good Manufacturing Practice (GMP) programs, we have analyzed products produced and offered by ready‐to‐eat food stores. Two hundred and seventy four samples of a wide variety of foods from 19 different shops were analyzed. Aerobic counts, total coliforms and yeast and molds were enumerated in each sample. Food stores were evaluated using a GMP check‐list. They were grouped in three classes: Class III, nonsatisfactory GMP; Class II, partially satisfactory GMP; and Class I, satisfactory GMP. From the results of microorganism counts in the Class I food shops the following maximum counts are proposed for cooked ready‐to‐eat foods: aerobic colony count: 105 cfu g−1. It is coincident with satisfactory microbiological quality of many category 3 foods drawn up by Public Health Laboratory Service (PHLS).