A new study found that the etiology of bacterial infections in acute exacerbations of chronic obstructive pulmonary disease could be determined through their associated comorbidities, a finding with relevance for clinical practice. The study, titled “Bacterial flora in the sputum and comorbidity in patients with acute exacerbations of COPD,” was published in the International Journal of Chronic Obstructive Pulmonary Disease.
Chronic obstructive pulmonary disease (COPD) covers a group of lung diseases, including chronic bronchitis (CB), emphysema phenotypes, and chronic obstructive airways disease. COPD is a frequent, preventable, and treatable respiratory condition, but a major cause of morbidity and mortality worldwide.
Respiratory infections caused by viruses or bacteria are responsible for up to 50%–70% of acute exacerbations in COPD patients. The existence of purulent sputum may suggest a bacterial etiology, or cause, for these flares, since 25%–50% of COPD patients’ lungs are colonized by potentially pathogenic microorganisms. Bacterial colonization has been associated with the frequency and severity of COPD exacerbations.
Most guidelines recommend the use of antibiotics when two or more of the Anthonisen’s criteria (i.e. increased dyspnea, increased sputum volume, and increased sputum purulence) are present. However, sputum purulence seems to be the main factor associated with infection. The type of antimicrobial drug used depends on the suspected microorganism, the severity of the COPD, and the presence of comorbidities, such as diabetes mellitus, liver cirrhosis, or heart disease. As a result, there is a need to establish if comorbidities have an association to the microorganism causing exacerbations. This will help clinicians to choose an antibiotic treatment less likely to lead to therapeutic failure and resistance.
In this study, the research team evaluated the comorbidities of patients, admitted to several Spanish Internal Medicine services from October 2009 to October 2010, to find clinical characteristics that might help a microbiological diagnosis. The researchers only included patients admitted with confirmed acute COPD exacerbations (AE-COPD). Briefly, the researchers analyzed the first 10 consecutive patients attended to in each of 70 participating hospitals to identify isolated bacteria in the patients’ sputum and to relate them to comorbidities and their association to mortality and hospital readmissions within the first three months after discharge.
The research team analyzed a total of 536 patients, of which 161 produced valid sputum. A potentially pathogenic microorganism was isolated from 88 subjects (16.4%). Researchers observed that the most frequently isolated microorganism was Pseudomonas aeruginosa (30.7%), followed by Streptococcus pneumoniae (26.1%), Enterobacteriaceae (20.4%), H. influenzae (15.9%), and M. catharralis (6.8%). None of these patients had Staphylococcus aureus. The isolation of P. aeruginosa (30.7%) was associated with a greater severity of the lung disease and other comorbidities such as heart failure and cerebrovascular disease. S. pneumoniae was associated with greater comorbidity according to a number of diseases, such as peripheral artery disease, hypertension, dyslipidemia, osteoporosis, and depression. For enterobacteria, the patients were younger, had less functional impairment, and were more likely to need non-invasive mechanical ventilation.
Overall, the researchers found that patients with AE-COPD and P. aeruginosa showed higher COPD severity, while those with S. pneumoniae had greater comorbidity. Moreover, diseases associated with COPD differed according to the microorganism isolated in the sputum.
Finally, these findings indicate that comorbidity can vary depending on the etiology of the bacterial exacerbation, and are relevant for clinical practice since they may help to decide the optimal antibiotic treatment for AE-COPD patients.