Enhanced Diagnostic Yield of Pleural Infection: The Role of Pleural Fluid Inoculation into Blood Culture Bottles

Abstract

Background: Pleural infection is a major complication of pneumonia and other thoracic diseases associated with high morbidity and mortality. Conventional pleural fluid culture has limited sensitivity, usually resulting in a negative culture because the patient has received some antibiotics or because the organism is a fastidious organism. When pleural fluid is inoculated directly into blood culture bottles, there may be higher diagnostic yield, lower time to pathogen detection, and better clinical decision-making. Objective: To determine if inoculation of pleural fluid into blood culture bottles would result in improved pathogen yield and detection time compared to conventional culture, and perform a spectrum and antibiotic susceptibility analysis of isolates to help guide empirical therapy. Methodology: A prospective cross-sectional study was conducted at Saidu Medical College and Teaching Hospital in Swat, Pakistan, from January 2023 to December 2023. 190 patients with pleural infection were eligible for the study. Pleural fluid samples were split to send for direct conventional culture and for inoculation of blood culture bottles. Data was analyzed with SPSS version 26. A P-value less than 0.05 was considered statistically significant. Results: For direct conventional culture, 58 (30.5%) pleural fluid samples had bacterial growth but for samples sent for blood culture bottles 108 (56.8%) were positive which is a relative increase of 26.3% detection rate depending on sample processing using blood culture bottles (P<0.001). The most common pathogens were Staphylococcus aureus (20%), Klebsiella pneumoniae (9.5%) and Acinetobacter spp (6.3%). Gram-positive isolates in the sample were 100% sensitive to vancomycin and linezolid. Gram-negative isolates had the highest sensitivity to colistin (76%) and significant resistance to carbapenems (61% resistant) and high resistance to cephalosporins (>70% resistant). Conclusion: Inoculation of pleural fluid into blood culture bottles enhances pathogen recovery and time to detection when compared with conventional culture methods.