Microbiological Characteristics and Predictive Factors for Mortality in Pleural Infection: A Single-Center Cohort Study in Korea

BACKGROUND Identification and understanding of the pathogens responsible for pleural infection is critical for appropriate antibiotic treatment. This study sought to determine the microbiological characteristics of pleural infection and to identify potential predictive factors associated with mortality. METHODS In this retrospective study, we analyzed patient data from 421 cases of parapneumonic effusion. A total of 184 microorganisms were isolated from 164 patients, using two culture systems: a standard method and a method using pairs of aerobic and anaerobic blood culture bottles. RESULTS The most frequently isolated microorganisms were streptococci (31.5%), followed by staphylococci (23.4%), gram-negative bacteria (18.5%) and anaerobes (10.3%). Streptococci were the main microorganisms found in standard culture (41.9%) and community-acquired infections (52.2%), and were susceptible to all antimicrobial agents in drug sensitivity testing. Staphylococci were the most frequently isolated pathogens in blood cultures (30.8%) and hospital-acquired infections (38.3%), and were primarily multidrug-resistant (61.8%). In multivariate analysis, the following were significant predictive factors for 30-day mortality among the total population: CURB-65 ≥ 2 (aOR 5.549, 95% CI 2.296-13.407, p<0.001), structural lung disease (aOR 2.708, 95% CI 1.346-5.379, p = 0.004), PSI risk class IV-V (aOR 4.714, 95% CI 1.530-14.524, p = 0.007), no use of intrapleural fibrinolytics (aOR 3.062, 95% CI 1.102-8.511, p = 0.014), hospital-acquired infection (aOR 2.205, 95% CI 1.165-4.172, p = 0.015), age (aOR 0.964, 95% CI 0.935-0.994, p = 0.018), and SOFA score ≥2 (aOR 2.361, 95% CI 1.134-4.916, p = 0.022). CONCLUSION In this study, common pathogens causing pleural infection were comparable to previous studies, and consisted of streptococci, staphylococci, and anaerobes. CURB-65 ≥2, structural lung disease, PSI risk class IV-V, no use of intrapleural fibrinolytics, hospital-acquired infection, older age, and SOFA score ≥ 2 are potential predictors of mortality in pleural infection.