Bacterial etiology and pneumococcal urinary antigen in moderate exacerbation of chronic obstructive pulmonary disease

BACKGROUND: This study aimed to establish nationwide data for the distributions of typical and atypical bacterial pathogens in Korean patients with moderate acute exacerbations of chronic obstructive pulmonary disease (AECOPD) and evaluate the clinical usefulness of a urinary antigen test (UAT) to detect Streptococcus pneumoniae. METHODS: This study was a post hoc analysis of a randomized controlled trial designed to compare oral zabofloxacin with moxifloxacin for treating outpatients with moderate AECOPD. From clinics across South Korea, 342 subjects with AECOPD were enrolled, and their blood, sputum, and urine samples were collected at baseline. A serologic test, sputum culture and polymerase chain reaction (PCR), and UAT were performed to identify bacterial pathogens. Bacterial prevalence and regional distributions were analyzed. The patients’ characteristics and clinical response between UAT-positive and UAT-negative groups were compared, as were the Streptococcus pneumoniae detection rates using conventional sputum culture and PCR versus UAT. RESULTS: The most commonly isolated pathogen was Haemophilus influenzae (30.3%), followed by Streptococcus pneumoniae (24.7%) and Pseudomonas aeruginosa (14.0%), with no significant regional differences in bacterial distribution. Patients with positive UAT for Streptococcus pneumoniae showed no clinical failure when treated with respiratory quinolone (0.0%), whereas 11.8% of patients with negative UAT showed clinical failure (P=0.037). UAT showed moderate agreement with sputum culture by kappa coefficient (κ=0.476). CONCLUSIONS: The bacterial prevalence in patients with moderate AECOPD in South Korea showed correlations with the global prevalence, without significant regional differences. In outpatient settings, UAT has the potential to be used as a supplemental tool with sputum culture as a guide for determining the suspicion of bacterial exacerbation.