Analysis of the bacterial community in chronic obstructive pulmonary disease sputum samples by denaturing gradient gel electrophoresis and real-time PCR

BACKGROUND The Global Initiative defines COPD for chronic obstructive lung disease as an entirely preventable and treatable disease characterized by sputum production, bacterial colonisation, neutrophilic bronchial airway inflammation and poor health status. The World Health Organization (WHO) estimates that COPD will become the fourth-most common cause of death worldwide, just behind ischemic heart disease, cerebrovascular disease and HIV/AIDS, by 2030. The aim of this study was to determine the main structure feature of sputum potentially pathogenic microorganisms in subjects with COPD during the clinical stable state. METHODS We employed a molecular genetics-based investigation of the bacteria community, including DNA isolation, PCR amplification and DGGE profiling. PCR-denaturing gradient gel electrophoresis (DGGE) with universal primers targeting the V3 region of the 16S rRNA gene was employed to characterize the overall COPD patient sputum microbiota composition, and some excised gel bands were cloned for sequencing. Real-time PCR was further utilized to quantitatively analyze the subpopulation of microbiota using group-specific primers targeting Streptococcus pneumoniae, Klebsiella pneumoniae, Pseudomonas aeruginosa. RESULTS The DGGE profiles of two groups displayed significant differences between COPD and healthy groups (P < 0.05). Real-time PCR revealed significant increases of Streptococcus pneumoniae, Klebsiella pneumoniae and Pseudomonas aeruginosa (P < 0.05) in the COPD group compared with the healthy group. CONCLUSION This study revealed strong relationship between alterations of sputum microbiota and COPD. By determining the content of several types of bacteria, we can provide evidence to aid in the diagnosis and treatment of COPD.