Fig. 1
Levels of water contamination by Legionella [9]
| Number of Legionella spp. in 100 ml of hot water | Assessment of contamination |
|---|---|
| <100 | lack/minimal (GROUP A) |
| >100 | medium (GROUP B) |
| >1000 | high (GROUP C) |
| >10 000 | very high (GROPUP D) |
Comparison of the mean number of L_ pneumophila colonies (CFU) isolated from water samples in 2009–2013 and 2014–2016
| Year | Total number of water samples | Mean number of L. pneumophila CFU | Median | Standard deviation (SD) | Standard error (SE) |
|---|---|---|---|---|---|
| 2009–2013 | 4747 | 2574 | 77 | 119 | 102 |
| 2014–2016 | 2765 | 1541 | 118 | 381 | 192 |
Number of hot water samples tested in 2014–2016 according to accepted criteria of contamination
| Year | Number of water samples | GROUP A number/percentage of all water samples | GROUP B number/percentage of all water samples | GROUP C number/percentage of all water samples | GROUP D number/percentage of all water samples |
|---|---|---|---|---|---|
| 2014 | 832 | 542 (65.2%) | 187 (22.5%) | 85 (10.2%) | 18 (2.1%) |
| 2015 | 711 | 518 (72.9%) | 142 (19.9%) | 46 (6.5%) | 5 (0.7%) |
| 2016 | 1222 | 901 (73.7%) | 172 (14.2%) | 134 (10.9%) | 15 (1.2%) |
| Total samples in 2009–2013 | 2765 | 1961 (71.0%) | 501 (18.1%) | 265 (9.6%) | 38 (1.3%) |
Mean number of L_ pneumophila colonies isolated from hot water samples in 2009–2013
| Year | Number of water samples | Mean number of L. pneumophila colonies (CFU/100 ml) | Median | Standard deviation (SD) | Standard error (SE) |
|---|---|---|---|---|---|
| 2009 | 610 | 7134 | 150 | 481 | 525 |
| 2010 | 985 | 1316 | 98 | 346 | 350 |
| 2011 | 1052 | 921 | 60 | 263 | 264 |
| 2012 | 1642 | 3165 | 79 | 195 | 157 |
| 2013 | 458 | 333 | 25 | 120 | 170 |
| Values for the period 2009–2013 | Total: 4747 | 2574 | 77 |
Number of hot water samples tested in 2009–2013 according to accepted criteria of contamination
| Year | Number of water samples | GROUP A number/percentage of all water samples | GROUP B number/percentage of all water samples | GROUP C number/percentage of all water samples | GROUP D number/percentage of all water samples |
|---|---|---|---|---|---|
| 2009 | 610 | 433 (71%) | 108 (17.8%) | 56(9.1%) | 13(2.1%) |
| 2010 | 985 | 827 (84%) | 110 (11.1%) | 43 (4.4%) | 5 (0.5%) |
| 2011 | 1052 | 920 (87.5%) | 82 (7.8%) | 47 (4.5%) | 3 (0.2%) |
| 2012 | 1642 | 1393 (84.9%) | 160 (9.7%) | 82 (5%) | 7(0.4%) |
| 2013 | 458 | 394 (86.0%) | 55 (12.0%) | 9 (2.0%) | 0 |
| Total samples in 2009–2013 | 4747 | 3967 (83.6%) | 515 (10.8%) | 237 (5%) | 28 (0.6%) |
Mean number of L_ pneumophila colonies isolated from hot water samples in 2014–2016
| Year | Number of water samples | Mean number of L. pneumophila colonies (CFU/100 ml) | Median | Standard deviation (SD) | Standard error (SE) |
|---|---|---|---|---|---|
| 2014 | 832 | 1611 | 79 | 405 | 359 |
| 2015 | 711 | 859 | 110 | 277 | 263 |
| 2016 | 1222 | 2153 | 210 | 449 | 352 |
| Values for the period 2014–2016 | Total: 2765 | 1541 | 118 | 381 | 192 |