Table 4 Characteristics of patients with defined aetiology, comparing monomicrobial and polymicrobial pneumonia

Demographics

   Age (years)

61.6 ± 17.7

63.5 ± 14.1

0.48

   Sex (male)

106 (68%)

23 (59%)

0.31

   Current smoking

46 (30%)

13 (35%)

0.53

   Current alcohol abuse

32 (21%)

12 (33%)

0.11

Previous antibiotic

30 (22%)

2 (7%)

0.051

Influenza vaccine

50 (39%)

9 (35%)

0.65

Pneumococcal vaccine

20 (16%)

2 (8%)

0.29

Inhaled corticosteroid

29 (19%)

11 (31%)

0.10

Systemic corticosteroid

11 (7%)

4 (12%)

0.34

Co-morbidity

   Chronic respiratory disease

50 (32%)

21 (54%)

0.011

   Chronic cardiovascular disease

21 (14%)

1 (3%)

0.068

   Diabetes mellitus

26 (17%)

4 (11%)

0.40

   Neurological disease

19 (12%)

9 (25%)

0.052

   Chronic renal disease

10 (7%)

2 (6%)

0.84

   Chronic liver disease

9 (6%)

5 (13%)

0.11

Clinical findings

   Fever

132 (84%)

27 (69%)

0.034

   Diastolic blood pressure (mmHg)

68.0 (20.0)

70.0 (22.0)

0.38

   Systolic blood pressure (mmHg)

120.0 (48.0)

121.0 (63.0)

0.23

Laboratory findings

   Creatinine (mg/dl)

1.2 (0.8)

1.3 (0.7)

0.57

   C-reactive protein level (mg/dl)

25.2 (20.3)

26.5 (11.6)

0.24

   White blood cell count (10⁹ cells/l)

13.1 (12.1)

9.5 (13.4)

0.019

   Oxygen saturation (%)

93 (7.9)

92.0 (7.3)

0.78

   PaO₂/FIO₂

254.3 (84.6)

247.6 (104.8)

0.38

Inappropriate empirical treatment

15 (10%)

15 (39%)

< 0.001

Pneumonia severity index

   I to III

44 (29%)

10 (28%)

0.89

   IV

60 (40%)

8 (22%)

0.053

   V

48 (32%)

18 (50%)

0.037

Severe CAP

94 (68%)

31 (86%)

0.029

Bacteraemia

47 (32%)

14 (39%)

0.45

Multilobar infiltration

74 (47%)

27 (69%)

0.013

Pleural effusion

36 (23%)

9 (24%)

0.94

Mechanical ventilation

60 (43%)

21 (62%)

0.047

ARDS criteria

6 (4%)

12 (31%)

< 0.001

Septic shock

38 (24%)

14 (36%)

0.14

Length of hospital stay (days)

12.0 (11.0)

15.0 (10.0)

0.082

Thirty-day mortality

17 (11%)

8 (21%)

0.10