A Prospective Study of Bacteriological Etiology in Hospitalized Acute Exacerbation of COPD Patients: Relationship with Lung Function and Respiratory Failure

Abstract

Objectives: Bacterial infections are the major cause of acute exacerbation of COPD (AE-COPD). The relationship between lung functions and respiratory failure (arterial blood gas parameters) with the etiology of AE-COPD has not been clearly understood. We conducted this study to determine the bacterial profile in AE-COPD and to identify the associated risk factors and drug sensitivity pattern.

Material and methods: Seventy-two patients hospitalized for AE-COPD were prospectively evaluated. Quantitative sputum culture, blood gas analysis, and drug sensitivity testing were performed at the time of admission, and pulmonary function testing was performed 6 weeks after discharge as per standard guidelines.

Results: Bacterial pathogens were isolated in 34 (47.22%) cases. Pathogens isolated were Pseudomonas aeruginosa (38.23%), Klebsiella pneumoniae (29.41%), Staphylococcus aureus (23.53%), Streptococcus pneumoniae (5.88%), and Acinetobacter spp. (2.94%). Isolation of bacterial pathogen was observed in patients with advancing age (p=0.02), frequent exacerbations (p<0.001), systemic steroid use (p=0.005), and deranged lung function (p=0.02). Binary logistic regression analysis revealed that higher partial pressure of carbon dioxide (PaCO2) was independently associated with isolation of K. pneumoniae (p=0.025) and P. aeruginosa (p=0.001). Additional independent factors that favor isolation of K. pneumoniae were age >55 years (p=0.017) and systemic steroid use (p=0.017). Antibiotic sensitivity testing showed that ciprofloxacin and piperacillin/tazobactum were effective in 27/34 (79.41%) of isolates followed by gentamycin in 26/34 (76%).

Conclusion: Hypercapnic respiratory failure is an independent risk factor for isolation of K. pneumoniae and P. aeruginosa in addition to advanced age and systemic steroid use. These findings may be an important adjunct in deciding the initial antibiotic therapy.

Keywords: Chronic obstructive pulmonary disease; acute exacerbation; bacteria; lung function; respiratory failure.

Figure 1

Pathogenic microorganisms isolated from sputum culture PPMs: potentially pathogenic microorganisms

Figure 2

FEV1 represented as mean value, SD and range for PPMs separately and non-PPMs as whole group. Horizontal bars represent mean values, boxes represent mean±SD, and vertical bars represent 95% CI PPMs: potentially pathogenic microorganisms; FEV1: forced expiratory volume in 1 second; SD: standard deviation; CI: confidence interval *Acinetobacter was recovered in one sputum sample, so represent as single bar