Table 1 Growth of Legionella spp. and total bacterial count (p-value compares results of water samples from old filters to results from new filters)
number of Legionella positive samples | number of samples >100 CFU per mL in total bacterial count at 22°C | number of samples >100 CFU per mL in total bacterial count at 36°C | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
unfiltered water (n = 60) | 29 (48.3%) | 18 (30.0%) | 33 (55.0%) | |||||||
old filter (n = 20) | new filter (n = 40) | p-value | old filter (n = 20) | new filter (n = 40) | p-value | old filter (n = 20) | new filter (n = 40) | p-value | ||
filtered water at different usage intervals | 7 days | 0 (0.0%) | 1 (2.5%) | 1.000 | 3 (15.0%) | 0 (0.0%) | 0.033 | 2 (10.0%) | 0 (0.0%) | 0.107 |
14 days | 0 (0.0%) | 0 (0.0%) | 1.000 | 9 (45.0%) | 10 (25.0%) | 0.146 | 4 (20.0%) | 8 (20.0%) | 1.000 | |
21 days | 0 (0.0%) | 0 (0.0%) | 1.000 | 10 (50.0%) | 18 (46.2%)** | 0.787 | 9 (45.0%) | 20 (50.0%) | 0.788 | |
28 days | 0 (0.0%) | 0 (0.0%)* | 1.000 | 9 (45.0%) | 25 (64.1%)* | 0.177 | 14 (70.0%) | 27 (69.2%)* | 1.000 | |