Comparison of methods for recovering Vibrio cholerae O1 from ice

Alkaline peptone water (1% peptone, 1% NaCl, pH 8.5) and Trypticase soy yeast extract broth (TSYB) supplemented with 2.5% NaCl (pH 8.5) or 1% NaCl (pH 7.5) were evaluated as enrichment broths for the isolation of Vibrio cholerae O1 from ice. Thirty samples of sterile and nonsterile mineral water were inoculated with cell suspensions of this bacterium, quickly frozen, and stored for 3 days at--18 degrees C. After thawing, samples were analyzed by a three-tube most-probable-number technique. Incubation in TSYB with 2.5% NaCl (pH 8.5) for 18 h at 37 degrees C yielded the highest recovery of V. cholerae O1 cells (P < 0.05), a result that might be attributable to the nutrients and to the NaCl concentration of the TSYB, both of which would promote V. cholerae O1 growth and prevent the growth of competitive microbiota.