Table 4 Risk factors associated with Legionella isolation in univariate analysis

Water temperature°C

≥20°C - ≤ 45°C

48 (13.3)

314 (86.7)

1.98

1.30 - 3.03

< 0.001

vs.

<20°C or > 45°C

47 (7.2)

609 (92.8)

Residual free chlorine concentration mg/L

< 0.5

90 (12.9)

610 (87.1)

5.3

2.63 - 10.65

< 0.001

vs.

≥ 0.5

9 (2.7)

323 (97.3)

Potability of water according to regulation

Not potable water

9 (25.0)

27 (75.0)

4.48

1.87 - 10.74

0.001

vs.

Potable water

21 (6.9)

282 (93.1)

No continuous vs. continuous hyperchlorination

No continuous hyperchlorination

15 (27.3)

40 (72.7)

6.41

3.10 - 13.26

< 0.001

vs.

Continuous hyperchlorination

23 (5.5)

393 (94.5)

Before vs. shock hyperchlorination at 15 days

Before shock hyperchlorination

43 (21.1)

161 (78.9)

3.17

1.70 - 5.92

< 0.001

vs.

Shock hyperchlorination at 15 days

15 (7.8)

178 (92.2)

Before vs. shock hyperchlorination at 30 days

Before shock hyperchlorination

43 (21.1)

161 (78.9)

7.43

3.08 - 17.94

< 0.001

vs.

Shock hyperchlorination at 30 days

6 (3.5)

167 (96.5)

Before vs. continuous hyperchlorination

Before shock hyperchlorination

43 (21.1)

161 (78.9)

4.56

2.66 - 7.82

< 0.001

vs.

Continuous hyperchlorination

23 (5.5)

393 (94.5)

Continuous vs. shock hyperchlorination at 30 days

Continuous hyperchlorination

23 (5.5)

393 (94.5)

1.63

0.65 - 4.07

0.15

vs.

Shock hyperchlorination at 30 days

6 (3.5)

167 (96.5)