Effect of Bronchial Colonisation on Airway and Systemic Inflammation in Stable COPD

Figures & data

Table 1.  Sociodemographic and sputum characteristics (microbiology, cytology and inflammatory markers) of PAC-COPD patients (n = 133)*

Patient characteristics
Age (years), mean (SD)	70 (9)
Males, n (%)	124 (93)
Smoking pack-years, median (P25-P75)	67 (43–102)
Current smoker, n (%)	35 (27)
Exacerbation last year ≥1, n (%)	45 (34)
MMRC dyspnoea scale, mean (SD)	2.7 (1.3)
FEV1 post-BD% pred, mean (SD)	52 (16)
BMI (kg/m2), mean (SD)	28 (5)
6MWD (m), median (P25-P75)	421 (369–457)
BODE index score, median (P25-P75)	3 (2–4)
SGRQ total score, mean (SD)	37 (18)
Inhaled corticosteroid treatment, n (%)	88 (66)
Sputum characteristics
Cell viability (%), median (P25-P75)	80 (65–90)
Neutrophils/ml ×106, median (P25-P75)	6.4 (1.7–17.1)
Neutrophils%, median (P25-P75)	72 (48–84)
IL-1β (pg/ml), median (P25-P75)	209 (52–695)
IL-6 (pg/ml), median (P25-P75)	124 (54–259)
IL-8 (x103) (pg/ml), median (P25-P75)	11 (4–16)
Colonised, n (%)	39 (29)
Polymicrobial cultures, n (%)	8 (6)
Bacterial load ×106 (cfu/ml), median (P25-P75)†	8.1 (1.0–40.0)
Haemophilus influenzae	22 (17)
Pseudomonas aeruginosa	8 (6)
Moraxella catarrhalis	6 (4.5)
Streptococcus pneumoniae	5 (4)
Other PPMs‡	6 (4.5)

*Patients with representative sputum samples according to percentage of squamous cells≤20%.

†In patients with a positive culture for PPMs. Expressed as ×106 cfu/ml. PPM showing a higher load considered for patients with polymicrobial cultures.

‡Staphylococcus aureus and enterobacteria.

Definition of abbreviations: SD = standard deviation; MMRC = modified Medical Research Council; BD = bronchodilator; FEV1 = forced expiratory volume in 1 second; BMI = body mass index; 6MWD = 6-minute walking distance; BODE = body-mass index (B), degree of airflow obstruction (O) and dyspnoea (D), and exercise capacity (E); PPMs = potential pathogenic microorganisms; cfu = colony forming units; IL = interleukin.

Some cases had missing values for certain variables: 3 patients cumulative smoking in pack-years; 8 6MWD; 8 BODE index; 8 bacterial load values.

Table 2.  Patient characteristics, sputum characteristics and plasma inflammatory markers according to bronchial colonisation*, in PAC-COPD patients (n = 133)

	No. colonised n = 94	Colonised n = 39	P-Value
Patient characteristics
Age (years), mean (SD)	69 (9)	70 (8)	0.669
Smoking pack-years, median (P25-P75)	58 (36–90)	80 (56–116)	0.007
Current smoker, n (%)	24 (27)	11 (28)	0.829
Chronic phlegm, n (%)	58 (62)	25 (64)	0.795
Exacerbation last year ≥1, n (%)	29 (31)	16 (41)	0.259
MMRC dyspnoea scale, mean (SD)	2.7 (1.4)	2.8 (1.3)	0.481
FEV1 post-BD% pred, mean (SD)	52 (17)	52 (14)	0.982
BMI (kg/m2), mean (SD)	28 (5)	28 (4)	0.913
6MWD (m), median (P25-P75)	421 (374–461)	422 (367–452)	0.783
BODE index score, median (P25-P75)	3 (2–4)	3 (2–3)	0.806
SGRQ total score, mean (SD)	35 (18)	40 (20)	0.206
Inhaled corticosteroid treatment, n (%)	64 (68)	24 (62)	0.468
Sputum characteristics
Total cells/ml ×106, median (P25-P75)	13 (4–23)	9 (4–22)	0.553
Neutrophils/ml ×106, median (P25-P75)	7 (2–18)	6 (2–13)	0.786
Eosinophils/ml ×106, median (P25-P75)	0.1 (0–0.3)	0.2 (0–0.7)	0.015
Neutrophils%, median (P25-P75)	71 (48–82)	75 (45–87)	0.524
Eosinophils%, median (P25-P75)	1 (0–3)	2 (0–5)	0.015
Eosinophils ≥3%, n (%)	22 (23)	16 (41)	0.041
IL-1β (pg/ml), median (P25-P75)	154 (41–477)	462 (121–993)	0.002
IL-6 (pg/ml), median (P25-P75)	109 (50–197)	145 (71–414)	0.047
IL-8 (x103) (pg/ml), median (P25-P75)	8 (3–15)	1315 (9–19)	0.002
Plasma inflammatory markers
IL-6 (pg/ml), median (P25-P75)	1.1 (0.5–2.0)	1.1 (0.6–2.0)	0.985
IL-8 (pg/ml), median (P25-P75)	4.2 (3.3–5.5)	4.7 (3.1–7.2)	0.173
TNF-α (pg/ml), median (P25-P75)	0.2 (0–0.5)	0.3 (0–0.7)	0.589
CRP (mg/l), median (P25-P75)	3.5 (1.7–5.4)	6.5 (2.5–8.5)	0.016
CRP > 7.06 mg/l, n (%)	16 (18)	14 (36)	0.030
Fibrinogen (g/l), median (P25-P75)	3.9 (3.2–4.5)	4.0 (3.5–4.6)	0.204

*Bronchial colonisation defined as a sputum culture positive for Haemophilus influenzae, Pseudomonas aeruginosa, Streptococcus pneumoniae, Moraxella catarrhalis, Staphylococcus aureus or enterobacteria.

Definition of abbreviations: IL = interleukin; TNF-α = tumour necrosis factor-α; CRP = C-reactive protein.

Some cases had missing values for certain variables: 3 patients cumulative smoking in pack-years; 8 6MWD; and 8 BODE index. Values were missing for plasma IL-6 in 7 cases, for plasma IL-8 in 6, for TNF-α in 5, for CRP in 6, and for fibrinogen in 5.

Table 3.  Risk factors for high levels of plasma C-reactive protein (CRP) in PAC-COPD patients (n = 133)

	CRP ≤ 7.06 mg/l	CRP > 7.06 mg/l	Crude OR (95% CI)	P
n	97	30
Age yrs, mean (SD)	69 (8)	71 (9)	1.03 (0.98–1.09)	= .190
Males, n (%)	91 (94)	28 (93)	1.08 (0.21–5.67)	= .924
Pack-year (over median), n (%)	52 (55)	17 (57)	1.06 (0.46–2.42)	= .897
Current smoker, n (%)	25 (27)	8 (27)	1.00 (0.40–2.54)	= .994
Chronic phlegm, n (%)	60 (62)	18 (60)	0.93 (0.40–2.14)	= .860
Exacerbation last year ≥1, n (%)	32 (33)	13 (43)	1.55 (0.67–3.59)	= .302
≥2 Co-morbidity†, n (%)	59 (61)	17 (57)	0.84 (0.37–1.93)	= .685
Cardiac co morbidity‡, n (%)	14 (14)	7 (23)	1.80 (0.65–4.99)	= .256
FEV1 post-BD% pred, m (SD)	54 (17)	48 (11)	0.97 (0.94–1.00)	= .050
BMI (kg/m2), m (SD)	28 (5)	28 (4)	0.99 (0.90–1.08)	= .770
SGRQ total score, mean (SD)	35 (18)	39 (18)	1.01 (0.99–1.04)	= .299
Bronchial colonisation*, n (%)	25 (26)	14 (47)	2.52 (1.08–5.89)	= .033

†From Charlson index ≥1 means one or more in addition to COPD.

‡Cardiac co-morbidity: Myocardial infarction and/or heart failure.

*Bronchial colonisation defined as a sputum culture positive for Haemophilus influenzae, Pseudomonas aeruginosa, Streptococcus pneumoniae, Moraxella catarrhalis, Staphylococcus aureus or enterobacteria.

Definition of abbreviations: SD = standard deviation; FEV1 = forced expiratory volume in one second; BMI = body mass index.

Figure 1.  Scarplot of total bacterial count (colony forming units (cfu)/ml−1) and sputum interleukin (IL)-8 (pg/ml−1) (Spearman's correlation coefficient r = 0.529, p = 0.024) in patients colonised by Haemophilus influenzae.

Table 4.  Species-specific relationships of bronchial colonisation (n = 133)

	No. colonised	H. influenzae	P value	Other PPMs&	P-value
No. of patients	94	22		17
Bacterial load (x106) (cfu/ml), median (P25-P75)†	–	5.4 (1–12)	–	10 (1–100)
Patient characteristics
FEV1 post-BD% pred, mean (SD)	52 (17)	51 (15)	0.647	55 (11)	0.558
Smoking pack-years, median (P25-P75)	58 (36–90)	103 (62–138)	0.003	68 (56–90)	0.322
Exacerbation last year ≥1, n (%)	29 (31)	7 (32)	0.930	9 (53)	0.077
SGRQ total score, mean (SD)	35 (17)	42 (20)	0.105	37 (20)	0.807
SGRQ activity score, mean (SD)	47 (24)	58 (26)	0.049	47 (24)	0.918
SGRQ impact score, mean (SD)	25 (18)	34 (18)	0.041	27 (21)	0.751
SGRQ symptoms score, mean (SD)	47 (19)	49 (14)	0.592	48 (22)	0.827
Sputum and plasma inflammatory markers
Sputum IL-1β (pg/ml), median (P25-P75)	154 (41–477)	746 (121–1742)	0.001	279 (168–695)	0.202
Sputum IL-8 (×103) (pg/ml), median (P25-P75)	8 (3–15)	16 (11–22)	0.001	13 (6–16)	0.240
Plasma CRP (mg/l), median (P25-P75)	3.5 (1.7–5.4)	6.5 (2.5–7.7)	0.050	6.0 (2.7–14.0)	0.085

*Other potentially pathogenic microorganisms (PPMs) were Pseudomonas aeruginosa, Streptococcus pneumoniae, Moraxella catarrhalis, Staphylococcus aureusoand enterobacteria, in patients with negative cultures for Haemophilus influenzae.

†Expressed as ×106 cfu/ml. PPM showing a higher load considered for patients with polymicrobial cultures.

Patients colonised by H.influenzae were compared with no colonised patients. Patients colonised by other PPMs similarly compared with no colonised patients. Comparisons were performed using a chi-square, Fisher exact, t or Kruskal-Wallis tests, as required, using no colonised patients as the reference.

Definition of abbreviations: PPM = potentially pathogenic microorganisms; SGRQ = St. George's Respiratory Questionnaire.