The impact of direct inoculation of ascites into blood culture bottles on ascites culture positivity

Abstract Objective: Assess whether direct inoculation of ascites into blood culture bottles would improve ascites culture yield. Design: Pre-post-study. Setting: The study was performed at a quaternary academic medical center in Houston, Texas, including all inpatient and emergency department encounters. Patients: Ascites cultures collected from November 2020 to December 2022 were reviewed and screened for spontaneous bacterial peritonitis. Patients were excluded if a prior ascites culture from the same patient was already included in the study or if there was evidence of secondary bacterial peritonitis. Intervention: In the pre-intervention period, ascites cultures were collected into a sterile container and inoculated onto/into solid and liquid media. In the post-intervention period, ascites cultures were instead directly inoculated into bioMérieux© blood culture bottles at the bedside. Results: 114 patients met inclusion and exclusion criteria, 61 pre-intervention and 53 post-intervention. Overall ascites culture positivity was 15.8% (18/114), 11.5% (7/61) pre-intervention vs 20.8% (11/53) post-intervention. After adjusting for confounders, the intervention had a trend toward a significant effect on ascites culture positivity (P = 0.077). No significant differences were seen in time to positivity, hospital length of stay, or 30-day readmission. Conclusions: Direct inoculation of ascitic fluid into blood culture bottles led to a small increase in culture yield but lacked statistical significance. This lack of significance may be due to the study being underpowered. Further studies are required to investigate if this is due to procedural inefficiencies (eg, inadequate inoculation volumes) or pragmatic clinical practice considerations (ie, high rates of pre-culture antibiotics).