Validity of reducing blood culture incubation time for the BD BACTEC FX blood culture system considering microbiological and clinical aspects

A blood culture (BC) test is vital for diagnosing bacteremia in clinical practice. Although incubation time varies among automated BC systems, 4–5 days is deemed to be sufficient time for the BD BACTEC FX blood culture system. This study compared the clinical and microbiological characteristics of true-positive BC samples on day 5 with those within 4 days to reduce missed true bacteremia cases. We conducted a retrospective study of blood cultures from hospitalized patients between April 2020 and April 2023 at a tertiary care hospital in Japan. In total, 12,342 BC sets were collected from 6,567 patients. Gram-positive bacilli other than spp. and spp., non-, and yeasts other than spp. were detected more frequently in BC-positive patients on day 5 than in those within 4 days. The gastrointestinal tract was the portal of entry more frequently on day 5 than within 4 days (25 % vs. 4 %, p = 0.006). A 4-day incubation period is sufficient for the BD BACTEC FX blood culture system under routine conditions. However, a 5-day incubation period may be warranted when low pathogenicity is suspected or the gastrointestinal tract is suspected as the portal of entry.