The Only Blood Culture for Diagnosis of Bacteremia - Comparative Study of Practice

Overview

Current recommendations for the diagnosis of bacteremia based on the embodiment February-March blood cultures separated by a minimum interval of 30 minutes. Each blood culture comprises seeding a pair of aerobic and anaerobic vials inoculated each with 5 to 10 ml of blood. The sensitivity and specificity of this technique depends essentially on the amount of blood removed since there is a direct relationship between the volume of blood inoculated into each flask and the efficiency of the technique. A preliminary study conducted at the University Hospital of Caen found that 14-30% of patients depending on the services had received only one blood culture. In addition, at least four blood cultures in 24 hours were taken for 10 to 20% of patients. The practice of a single blood culture reduces the sensitivity of the analysis due to insufficient total amount of blood collected. The practice of too many blood cultures increases the risk of false positive (presence of contaminating bacteria), generates extra work for healthcare personnel (and laboratory) and represents a significant cost for an unproven benefit. The investigators propose to evaluate a single blood culture sampling technique with seeding 4 vials (2 aerobic and anaerobic 2).

Blood cultures will be collected from patients admitted with on of the following signs: fever (≥38.5°C), hypothermia (≤36°C), chills or shock. For the first blood culture, 40 mL of blood will be obtained aseptically by a single phlebotomy and equally distributed into two BacT/Alert FA aerobic bottles and two BacT/Alert FN anaerobic bottles (bioMérieux, La-Balme-les-Grottes, France). The four bottles will be labelled from one to four in the following order: aerobic-anaerobic-aerobic-anaerobic. Within the next 24 h, one to three other 20-mL blood cultures consisting of a single pair of aerobic and anaerobic bottles will have to be performed, spaced by a minimum of 30 minutes. Bottles will be incubated for 5 days or until positivity reported by the BacT/Alert 3D instrument.