Microbiologic analysis of bottled water - Is it safe for use with contact lenses?

Objective: To analyze commercially available bottled water as a possible so urce of microbial contamination of contact lenses. Methods: Two different lots of 23 brands of noncarbonated bottled water wer e tested for coliforms, total bacteria, fungi, and free-living amebae. A sa mple consisted of three separate 100-ml aliquots from one lot of each brand (46 samples). Aliquots were vacuum-filtered using a 0.45-mu m Nalgene anal ytical filter unit, and the membrane filter was placed on a filter pad in a Petri dish containing test medium. Plates were examined under a stereomicr oscope, and the number of colony-forming units (CFUs) was calculated for ea ch sample, To test for the presence of free-living amebae, three aliquots t otaling approximately 3800 ml were concentrated using 8-mu m filters, and t he filters were placed on non-nutrient agar with live Enterobacter aerogene s. To assess the possibility of contaminating contact lenses, etafilcon len ses were rinsed in 2-ml aliquots of four brands of bottled water and then c ultured. Results: Seventeen (37%) of 46 samples, representing 11 (48%) of 23 brands, contained viable microorganisms. Bacteria, including coliforms, were recov ered from 12 samples of 8 brands. Yeasts or molds were recovered from seven samples of five brands. Free-living amebae were isolated from two samples, and fresh-water algae were found in both samples of one brand. Nine (20%) of 46 samples, representing 7 (30%) of the 23 brands, had more than 500 CFU s per ml or contained coliforms. Sterile contact lenses became contaminated when exposed for 1 minute to two of four brands of water from which micro- organisms were recovered. Conclusion: Some bottled waters contain high numbers of potential ocular pa thogens. Bottled water is not safe for routine use with contact lenses.