Controlled comparison of the BacT/Alert and BACTEC 660/730 nonradiometric blood culture systems

Abstract

In a collaborative study at three university hospitals, the recovery of microorganisms and the speed of detection of microbial growth by the BacT/Alert (Organon Teknika Corporation, Durham, N.C.) and BACTEC 660/730 (Becton-Dickinson Diagnostic Instrument Systems, Sparks, Md.) nonradiometric blood culture systems were compared. A total of 5,918 comparisons were made between BacT/Alert aerobic and BACTEC NR 6A bottles and 5,992 comparisons were made between BacT/Alert anaerobic and BACTEC NR 7A bottles. Each bottle was inoculated with 5 ml of blood. The overall recoveries of microorganisms from the two aerobic bottles were comparable; members of the family Enterobacteriaceae were recovered more often from BacT/Alert aerobic bottles alone (P less than 0.001). The overall recoveries of microorganisms from the anaerobic bottles were not significantly different. Growth of Staphylococcus aureus (P less than 0.001), coagulase-negative staphylococci (P less than 0.01), streptococci (P less than 0.001), Escherichia coli (P less than 0.01), other members of the family Enterobacteriaceae (P less than 0.02), and Pseudomonas aeruginosa (P less than 0.05) was detected earlier in BacT/Alert aerobic bottles. Growth of S. aureus (P less than 0.001), coagulase-negative staphylococci (P less than 0.05), enterococci (P less than 0.01), Streptococcus pneumoniae (P less than 0.02), viridans group streptococci (P less than 0.05), E. coli (P less than 0.001), Klebsiella pneumoniae (P less than 0.01), and other members of the family Enterobacteriaceae (P less than 0.001) was detected earlier in BacT/Alert anaerobic bottles. In a system-versus-system comparison, more gram-positive cocci were recovered from the BACTEC system alone (P < 0.05), and more members or the family Enterobacteriaceae were recovered from the BacT/Alert system alone (P < 0.001). As a system, the BacT/Alert system detected growth of S. aureus (P < 0.001), coagulase-negative staphylococci (P < 0.01), streptococci (P < 0.001), E. coli (P < 0.001), other members of the familyEnterobacteriaceae (P < 0.001), and P. aeruginosa (P < 0.05) earlier than the BACTEC system did. Significantly fewer (40 versus 1,183) false-positive results occurred with the BacT/Alert system. We conclude that the BacT/Alert and BACTEC 660/730 nonradiometric systems are comparable for recovering clinically significant microorganisms form adult patients with bacteremia or fungemia, but that the BacT/Alert system detects microbial growth earlier than the BACTEC system does, with significantly fewer false-positive results.