Miravitlles et al. Respiratory Research 2010, 11:58 http://respiratory-research.com/content/11/1/58 Open Access RESEARCH BioMed Central © 2010 Miravitlles et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Research Colour of sputum is a marker for bacterial colonisation in chronic obstructive pulmonary disease Marc Miravitlles* 1 , Alicia Marín 2 , Eduard Monsó 3 , Sara Vilà 1 , Cristian de la Roza 4 , Ramona Hervás 3 , Cristina Esquinas 1 , Marian García 3 , Laura Millares 3 , Josep Morera 3 and Antoni Torres 5 Abstract Background: Bacterial colonisation in chronic obstructive pulmonary disease (COPD) contributes to airway inflammation and modulates exacerbations. We assessed risk factors for bacterial colonisation in COPD. Methods: Patients with stable COPD consecutively recruited over 1 year gave consent to provide a sputum sample for microbiologic analysis. Bronchial colonisation by potentially pathogenic microorganisms (PPMs) was defined as the isolation of PPMs at concentrations of ≥10 2 colony-forming units (CFU)/mL on quantitative bacterial culture. Colonised patients were divided into high (>10 5 CFU/mL) or low (<10 5 CFU/mL) bacterial load. Results: A total of 119 patients (92.5% men, mean age 68 years, mean forced expiratory volume in one second [FEV 1 ] [% predicted] 46.4%) were evaluated. Bacterial colonisation was demonstrated in 58 (48.7%) patients. Patients with and without bacterial colonisation showed significant differences in smoking history, cough, dyspnoea, COPD exacerbations and hospitalisations in the previous year, and sputum colour. Thirty-six patients (62% of those colonised) had a high bacterial load. More than 80% of the sputum samples with a dark yellow or greenish colour yielded PPMs in culture. In contrast, only 5.9% of white and 44.7% of light yellow sputum samples were positive (P < 0.001). Multivariate analysis showed an increased degree of dyspnoea (odds ratio [OR] = 2.63, 95% confidence interval [CI] 1.53-5.09, P = 0.004) and a darker sputum colour (OR = 4.11, 95% CI 2.30-7.29, P < 0.001) as factors associated with the presence of PPMs in sputum. Conclusions: Almost half of our population of ambulatory moderate to very severe COPD patients were colonised with PPMs. Patients colonised present more severe dyspnoea, and a darker colour of sputum allows identification of individuals more likely to be colonised. Background Exacerbations are the main cost driver in chronic obstructive pulmonary disease (COPD), have a negative impact on the clinical course of the patients and are asso- ciated with increased mortality [1-3]. Around 70% of exacerbations are infectious in nature, either bacterial, viral or mixed [4-7]. It has been shown that airway bacte- rial load in the stable state contributes to airway inflam- mation and modulates the character and frequency of exacerbations [8,9]. There is also evidence that bronchial colonisation influences the decline in lung function over time [10]. Different studies in which respiratory samples were obtained by the protected specimen brush (PSB) technique have shown a high prevalence of bronchial col- onisation in COPD patients [5,11,12]. However, the prac- tice of bronchoscopy to assess bronchial colonisation in routine clinical practice is not feasible and data that sup- port the use of sputum samples to identify patients colo- nised by potentially pathogenic microorganisms (PPMs) are required. Consequently, a cross-sectional study was designed to assess the frequency of bronchial bacterial colonisation using sputum samples and to identify risk factors for col- onisation in stable ambulatory patients with COPD. The * Correspondence: marcm@separ.es 1 Fundació Clínic. Institut D'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS). Ciber de Enfermedades Respiratorias (CIBERES), Barcelona, Spain Full list of author information is available at the end of the article