Title: Comparative Study of Pleural Fluid Culture in Standard Culture Bottle and Blood Culture Bottle for the Evaluation of Empyema
Authors: Sadakkathulla Unais Cholasseri, Thomas George Puthusseril, Davis Paul Chelangara
DOI: https://dx.doi.org/10.18535/jmscr/v5i8.148
Abstract
Background: Bacterial pleural infection has been a substantial clinical challenge since ancient times. Identification of the infecting bacteria by culture of pleural fluid is of great importance for clinical care. Inoculating pleural fluid into blood culture bottles at the bedside can potentially improve the yield of pleural fluid culture.
This study was done to assess whether addition of blood culture bottle sample to the standard bottle sample increases the rate of detection in pleural fluid culture for the evaluation of empyema.
Materials and Methods: A cross sectional observational study was conducted in patients with clinical presentation compatible with empyema with purulent pleural fluid drainage during thoracocentesis for a period of 1 year from 1st January 2013 to 31st December. Those having sputum positive tuberculosis were excluded. Two samples were collected in sterile bottle for standard culture and one sample in blood culture bottle from every patient enrolled into the study. The second standard culture was taken to assess whether the increase in yield was due to repetition of culture. All samples sent to microbiology laboratory of same institute. The standard bottle samples were subjected to Gram staining and inoculated to blood, MacConkey and chocolate agar. Blood culture bottle containing pleural fluid was incubated at 370 c for upto 7 days. A Gram stain was performed on any positive bottle and subculture was done to identify the organism. Identification of cultures were done by standard biochemical tests in microbiology laboratory. Further evaluation and management of patients done according to the department protocol
Results: A total of 60 patients were enrolled in the study.The standard laboratory culture of pleural fluid was positive in 19 (31.6%) cases. A second standard culture did not produce an increase in bacterial yield. Pleural fluid culture in blood culture bottle was positive in 24 (40%) cases. Addition of blood culture bottle culture to standard laboratory culture increased culture positivity by 8.4 (chi square value 41.7 with p <0.001). All cases which are culture positive in standard bottle were also positive in blood culture bottle. Klebsiella pneumoniae was the most common bacterium identified in pleural fluid culture. Blood culture bottle culture identified two extra cases of Pseudomonas aeruginosa, one case of Escherichia coli and Klebsiella pneumoniae, and a mixed infection case
Conclusion: Inoculating pleural fluid into blood culture bottles at the bedside increases the rate of bacterial pathogen identification in empyema, when compared to standard laboratory culture.
Keywords: Empyema, Blood culture bottle, Standard laboratory culture.
