Factors predicting bacterial involvement in severe acute exacerbations of chronic obstructive pulmonary disease.

Background: Strategies aiming at reducing antibiotic use are required in the intensive care unit (ICU). Although antibiotic treatment is recommended in patients with severe exacerbation of chronic obstructive pulmonary disease (COPD), a bacterial etiology is found in only a half of these patients.

Objectives: The aim of this study was to determine factors predicting bacterial isolation in severe acute exacerbations of COPD.

Methods: All patients with severe acute exacerbation of COPD requiring intubation and mechanical ventilation were included in this prospective observational cohort study. At ICU admission, information on endotracheal aspirate purulence and hyperthermia was collected. In all patients, Gram stain and quantitative endotracheal aspirate culture (positive at 10(6) cfu/ml) were performed. In addition, leukocyte count, C-reactive protein and procalcitonin (PCT) levels were measured.

Results: Ninety-eight severe acute exacerbations of COPD requiring intubation and mechanical ventilation were studied. Forty-nine bacteria were isolated at significant threshold in 40 exacerbations. Streptococcus pneumoniae (16%), methicillin-sensitive Staphylococcus aureus (16%) and Hemophilus influenzae (14%) were the most frequently isolated bacteria. PCT >0.5 ng/ml and positive Gram stain of endotracheal aspirate were independently associated with bacterial isolation in severe acute exacerbation of COPD. Positive Gram stain and PCT >0.5 ng/ml had a negative predictive value >95%. Similar results were found after excluding patients with prior antibiotic treatment.

Conclusion: Positive Gram stain of endotracheal aspirate and PCT >0.5 ng/ml are independently associated with bacterial isolation in severe acute exacerbation of COPD. These results could be helpful for future interventional studies aiming at reducing antibiotic use in these patients.