Purpose: This study was carried out in order to determine species of bacteria causing sepsis and the rate of false positives and negatives in the results obtained in the evaluation of blood cultures by the Bactec 9240 system. Method: For a period of one year, from September 1994 to September 1995, 8022 blood cultures which were taken by various clinics from patients with fever or sepsis were evaluated using the Bactec 9240 system. For this purpose, Bactec plus Aerobic/F and Bactec Peds plus/F vials were examined for 7 days. Identification of the bacteria was made using the Sceptor system. Results: Out of the 8022 blood cultures, 1763 were positive with the Bactec 9240 system and of these, 1727 grew in the subcultures (2.05% false positives). As a result of subculturing of the 6259 blood cultures negative in the Bactec system, various bacteria and fungi were isoleted in 11 cultures (0.18% false negatives). The majority of the bacteria isolated were Staphylococcus species. Besides this, out of the 1763 cultures that were positive with Bactec 9240, 19 (1.08%) were positive after the 5th day. Conclusion: The time involved in the evaluation of blood cultures is shortened when the Bactec 9240 system is used. Also, there is less contamination of the blood cultures since subculturing is done only once
