Survival and growth of Pseudomonas aeruginosa in natural mineral water: a 5-year study

A 5-year study was carried out on the growth curve of two strains of P. aer uginosa inoculated at a density of 10(2) cfu/ml into samples of natural min eral water with different levels of dissolved solids (TDS at 180 degrees C: 72.5 and 382 mg/l) and low organic content (TOC: 0.17 and 0.35 mg/l). The resulting growth curves were similar for both strains, with only slight dif ferences depending on the different amounts of dissolved solids in the wate r. After 4-5 days counts were increased by 3 log units. This level was main tained until 70-100 days from inoculation, after which a slow decrease bega n, culminating in the death of one of the strains after 5 years. No differe nce in recovery was observed between the method using direct inoculation on Cetrimide Agar and the resuscitation technique (preincubation in Tryptone Soya Agar followed by inoculation on Cetrimide Agar) in the exponential pha se of the growth curve. During the stationary and death phases, however, th e enrichment technique gave statistically slightly higher counts than the s elective technique, indicating the presence of damaged P. aeruginosa cells. The use of a resuscitation step when using Cetrimide Agar to assess bottle d water quality is recommended. (C) 1999 Elsevier Science B.V. All rights r eserved.