A survey of the microbiological quality of bottled water sold in the UK and changes occurring during storage

Eight brands of domestic and imported bottled water were microbiologically analysed within three hours of purchase at a local supermarket. Viable numbers of microorganisms were estimated on Plate Count Agar (PCA) and PCA diluted to quarter and tenth strengths (1/4 PCA and 1/10 PCA) and incubated at temperatures of 10, 15, 25 and 37°C. Plate count agar diluted to 1/4 and 1/10 incubated at 25°C yielded the highest initial counts, up to 104 cfu ml−1. Pseudomonas spp. was the predominant species. After 6 months of storage at room temperature (18–25°C), few quantitative and qualitative differences were found in the microflora.