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Infective exacerbations of chronic bronchitis: relation between bacteriologic etiology and lung function
1Department of Infectious Diseases and Immunology, Chest Clinic Heckeshorn, Berlin, Germany.
Study Objective:
In patients with severe COPD, acute infective exacerbations are frequent. Streptococcus pneumoniae and Haemophilus influenzae are the most commonly isolated bacteria in sputum cultures from these patients. We hypothesized that in patients with advanced disease, Gram-negative bacteria other than H influenzae play at least an equally important role.
Methods:
We evaluated clinical data and sputum culture results from 211 unselected COPD patients admitted to our hospital with an acute infective exacerbation of COPD. One hundred twelve patients fulfilled our protocol criteria of reliable microbiologic results and reproducible lung function tests; the patients were categorized according to the recently published three stages of severity.
Results:
Lung function tests revealed an FEV1 of > or =50% of the predicted value in 30 patients (stage I), an FEV1 of 35% to <50% of the predicted value in 30 patients (stage II), and an FEV1 of < or =35% of the predicted value in 34 patients (stage III). Bacteria were classified into three groups: group 1 contained S pneumoniae and other Gram-positive cocci; group 2, H influenzae and Moraxella catarrhalis; and group 3, Enterobacteriaceae and Pseudomonas spp. For all patients together, the most frequently isolated bacteria were group 3 organisms (Enterobacteriaceae and Pseudomonas spp, 48.2%), followed by group 1 organisms (S pneumoniae and other Gram-positive cocci, 30.4%), and group 2 organisms (H influenzae and M catarrhalis, 21.4%). In stage I patients, 14 of 30 had bacteria from group 1, seven of 30 had group 2, and nine of 30 had group 3. In stage II patients, eight of 30 had group 1 bacteria, 10 of 30 had group 2, and 12 of 30 had group 3. In stage III patients, 12 of 52 had group 1 bacteria, seven of 52 had group 2, and 22 of 52 had group 3. The three groups of bacteria causing infective exacerbations were unevenly distributed among the three severity stages of lung function (p=0.016).
Conclusion:
There is a correlation between deterioration of lung function and the bacteria isolated from patients with infective exacerbations of COPD. In acute infective exacerbations, Enterobacteriaceae and Pseudomonas spp are the predominant bacteria in patients with an FEV1 < or =35% of the predicted value.
Insights
In severe COPD, Gram-negative bacteria like Enterobacteriaceae and Pseudomonas spp. are common during acute infective exacerbations. These bacteria are predominant in patients with significantly reduced lung function (FEV1 < 35%).
Area of Science:
- Pulmonary Medicine
- Infectious Diseases
- Microbiology
Background:
- Acute infective exacerbations are frequent in severe chronic obstructive pulmonary disease (COPD).
- Streptococcus pneumoniae and Haemophilus influenzae are typically the most common bacterial culprits identified in sputum cultures.
- The role of other Gram-negative bacteria in advanced COPD exacerbations warrants further investigation.
Purpose of the Study:
- To investigate the role of Gram-negative bacteria, beyond H. influenzae, in severe COPD exacerbations.
- To determine the association between bacterial isolates and COPD severity stages.
- To test the hypothesis that Gram-negative bacteria play a significant role in advanced COPD.
Main Methods:
- Clinical data and sputum culture results were analyzed from 211 COPD patients hospitalized with acute infective exacerbations.
- 112 patients with reliable microbiologic and lung function data were categorized into three severity stages based on FEV1.
- Bacterial isolates were grouped: Group 1 (S. pneumoniae/Gram-positive cocci), Group 2 (H. influenzae/M. catarrhalis), and Group 3 (Enterobacteriaceae/Pseudomonas spp.).
Main Results:
- Group 3 organisms (Enterobacteriaceae and Pseudomonas spp.) were the most frequently isolated bacteria overall (48.2%).
- In patients with the most severe COPD (Stage III, FEV1 ≤ 35%), Group 3 bacteria were predominant (22/52 patients).
- The distribution of bacterial groups significantly differed across the three COPD severity stages (p=0.016).
Conclusions:
- A correlation exists between declining lung function and the specific bacteria isolated during COPD infective exacerbations.
- Enterobacteriaceae and Pseudomonas spp. are the predominant bacteria identified in patients with severe COPD (FEV1 ≤ 35%) experiencing acute infective exacerbations.