Abstract
Introduction: Exacerbation and comorbid pneumonia in COPD are critical events associated with disease progression and mortality. However, causative pathogens often remain unidentified despite clinical manifestations of airway infection. Although commensal organisms are frequent causes of these events, they may exist merely as colonizers. PCR method is quick and sensitive to detect microorganisms but is difficult in discriminating pathogens from colonizers. We have recently developed a semi-quantitative PCR method, HIRA-TAN, to detect microorganisms using an organism-to-human cell DNA copy number ratio as an index for their pathogenic role (2011 PLoS One).
Aim: To identify pathogenic bacteria in the airways of COPD by HIRA-TAN.
Methods: Between October 2009 and September 2010, sputum culture and HIRA-TAN analyses were performed in 254 patients suggestive of airway infection at Saitama Medical University Hospital. In this study we compared bacteria detected by the two methods in 107 patients who had airflow limitation (FEV1%<70) or significant emphysematous changes on Chest CT images.
Results: Sputum culture detected pathogenic bacteria in 51 cases (48%) out of 107, while HIRA-TAN identified those in 46 cases (43%). It was noted that the results were matched only in 21 cases between the two methods. HIRA-TAN detected S. pneumoniae in 22 cases whereas it was detected only in one and seven cases by sputum culture and the urine antigen test, respectively. In contrast sputum culture detected Haemophilus spp. other than H. influenzae in 16 cases.
Conclusions: These observations suggest that HIRA-TAN is useful to identify bacteria responsible for comorbid airway infections in COPD.
- © 2013 ERS