Comparison between Bactec Nr. 660® and a conventional 12‐tube blood culture system

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Abstract
The detection power of the automated blood culture system Bactec NR 660®, based on infrared detection of carbon dioxide in an agitated aerobic medium and a non‐agitated anaerobic medium, was compared with that of our conventional 12‐tube blood culture system. Of 1685 paired blood cultures, 258 (15.3%) were positive in one or both systems. Clinically relevant isolates were found in 11.5%. The dominating species were Escherichia coli (41%), followed by Staphylococcus aureus (14%) and Klebsiella spp. (8%). The Bactec® system detected 178 (10.6%) and the 12‐tube system 157 (9.3%) clinically relevant microorganisms after seven days' incubation. Significantly more clinically relevant isolates were detected by the Bactec® system alone as compared with the conventional system alone (40 versus 19, p < 0.01). The detection time was significantly shorter in the Bactec® system for all isolates and for E. coli and S. aureus separately (p < 0.01). 1.8% of the isolates in the Bactec® system and 2.1% in the 12‐tube system were considered clinically non‐relevant contaminants.