Comparative evaluation of BACTEC aerobic plus/F and septi-chek release blood culture media

Abstract

The BACTEC 9240 (Becton Dickinson, Sparks, Md.) automated blood culture system is based on the continuous monitoring of CO2 production by means of a fluorescent sensor attached to the bottom of culture vials. We compared the performance of the BACTEC aerobic Plus/F medium to that of the Septi-Chek Release medium (Becton Dickinson, Sparks, Md.), a manual biphasic blood culture system. Sets consisting of BACTEC aerobic Plus/F and Septi-Chek Release vials inoculated with similar volumes (7 ± 2 ml) were evaluated. In the laboratory, systems were equipped and analyzed according to the manufacturer's recommendations. The BACTEC and Septi-Chek vials were incubated at 35°C for 5 days. A total of 6,116 compliant sets were obtained from 1,972 adult patients (3.1 cultures per patient). Of these, 731 (12%) were culture positive, including 612 (10%) that yielded at least one pathogen, and 143 (2%) were considered to be contaminated. Of the 672 pathogenic organisms detected, 524 were isolated from the BACTEC aerobic Plus/F medium and 574 were isolated from the Septi-Chek Release medium, 428 organisms grew in both media, 96 organisms grew only in the BACTEC aerobic Plus/F medium, and 146 organisms grew only in the Septi-Chek Release medium (P = 0.001). Haemophilus spp. were isolated more often (P = 0.03) from the BACTEC aerobic Plus/F medium; however, more Streptococcus anginosus organisms (P = 0.02), members of the Enterobacteriaceae family (P < 0.03), and gram-negative anaerobes (P = 0.03) were isolated from the Septi-Chek Release medium. Pathogenic organisms were detected significantly earlier (P < 0.0001) with the BACTEC aerobic Plus/F medium in conjunction with the BACTEC 9240 instrument than with the Septi-Chek Release medium.