Recently, in The Second “Beijing–Hong Kong Forum for Infectious Disease Physicians” At the keynote symposium, Professor Wang Hui, Director of the Department of Laboratory Medicine at Peking University People’s Hospital, doctoral supervisor, advisor to the Antimicrobial Susceptibility Testing Subcommittee of the Clinical and Laboratory Standards Institute (CLSI), and member of the Microbiology and Immunology Branch of the Chinese Medical Association as well as deputy leader of its Clinical Microbiology Group, delivered a presentation titled “The Clinical Significance of Blood Cultures in the Diagnosis and Management of Bacteremia.”

Professor Wang Hui first pointed out that, with the widespread adoption of molecular techniques and biomarkers such as PCT, clinicians often overlook the importance of submitting specimens for microbiological testing. However, particularly in cases of bacteremia, the sensitivity of molecular methods and biomarkers is insufficient to replace conventional culture; they can only serve as adjunctive tools, while blood culture remains the gold standard for diagnosing bacteremia. At present, clinicians generally lack adequate awareness of the significance of blood culture, and their adherence to proper specimen‑collection practices is weak, resulting in a substantial gap between local and international standards in blood‑culture submission rates. Strengthening awareness of specimen submission and standardizing clinical sampling procedures are crucial for achieving accurate pathogen detection.

Subsequently, Professor Wang provided a detailed explanation of the key factors that influence the positive rate of blood cultures:

1. Indications for blood culture submission: Any patient with a fever ≥39.5°C or a body temperature ≥38.5°C, accompanied by any one of the following signs or symptoms—chills; pneumonia; placement of a central venous catheter for more than 5 days; white blood cell count >18,000/mm³; infective endocarditis; systolic blood pressure <90 mmHg; or an infection that cannot be explained by other causes—should promptly have venous blood drawn for blood culture.

2. Number of blood culture specimen collection sets To obtain accurate results, multiple sets of blood cultures are required. In adults, at least “two draws from four bottles” should be performed—meaning that two separate sets of blood cultures must be collected from two distinct puncture sites, with each set aliquoted into aerobic and anaerobic bottles, 8–10 mL per bottle, and clearly labeled with the “left” or “right” collection site. This approach can effectively increase the positive rate of blood cultures.

For suspected catheter‑related infections, clinicians should collect both peripheral blood and catheter‑tip blood samples, perform one set of blood cultures for each, and accurately document the time of collection and the site of venipuncture. This allows for a preliminary assessment of whether the infection is catheter‑related by comparing the time to positive growth between the catheter‑tip sample and the peripheral blood sample. Additionally, bacterial cultures of the catheter itself and its tip should be obtained at the time of catheter removal and after removal.

3. Blood culture specimens’ Timing of Blood Collection The optimal time for collecting blood cultures is during the peak of fever and chills; however, samples should still be obtained if this window is missed. It is preferable to obtain the first blood culture specimen before initiating antimicrobial therapy; if necessary, the initiation of antibacterial treatment may be delayed to allow for sampling.

4. Give priority to anaerobic bottle culture. Professor Wang conducted a survey of the positivity rates in 400 consecutive blood cultures and found that, within a single set, the anaerobic bottle accounted for 15% of positive results, while the aerobic bottle accounted for 37%. Culturing with anaerobic bottles enables rapid detection of highly pathogenic anaerobes, such as Bacteroides fragilis, Clostridium perfringens, and Peptostreptococcus species. These findings underscore the critical role of anaerobic bottles in pathogen diagnosis; therefore, anaerobic and aerobic bottles should be used in tandem to enhance the overall pathogen detection rate. 　

Key Points for Blood Culture Specimen Collection 　　

Diagnostic significance of bacterial identification from blood cultures

Finally, Professor Wang Hui analyzed extensive case data and outlined future directions for improving the quality of blood cultures. In addition to continuously monitoring both the quality and quantity of blood cultures, healthcare professionals should conduct follow-up blood cultures to assess treatment outcomes and identify the site of bloodstream infection. Even when patients with bacteremia receive adequate antimicrobial therapy and their symptoms improve, it remains essential to consider the relationship between specific pathogens and underlying conditions, and to leverage findings from follow-up blood cultures to pinpoint the source of the bloodstream infection, thereby guiding efforts to locate and address the primary focus of infection.