Detection of bacteremia by Difco ESP blood culture system

Abstract

In a multicenter study, the Difco ESP blood culture system (Difco Laboratories, Detroit, Mich.) was compared with the BACTEC NR660 system (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.). The ESP system monitors each blood culture bottle every 12 to 24 min to detect changes in oxygen consumption and gas production by microbes. Equal volumes of blood were inoculated into aerobic ESP-80A and BACTEC 6A, 16A, or PEDS Plus broths and anaerobic ESP-80N and BACTEC 7A or 17A broths and were incubated for up to 7 days. ESP bottles contain supplemented tryptic soy broth without antimicrobial agent-adsorbing resins. From 7,532 aerobic compliant sets, the ESP system detected 356 clinically significant positive cultures and the BACTEC NR660 system detected 329. From 6,007 anaerobic cultures, the ESP system detected 234 clinically significant positive cultures and the BACTEC NR660 system detected 198. In aerobic broths, 292 organisms were isolated from both systems and 78 organisms were isolated from the ESP system alone, whereas 54 organisms were isolated from the BACTEC NR660 system alone (P < 0.05). Among individual organisms, pneumococci were isolated significantly more often in ESP aerobic broths. In anaerobic broths, 180 organisms were isolated from both systems and 68 organisms were isolated from the ESP system alone, whereas 35 organisms were isolated from the BACTEC NR660 system alone (P < 0.05). Aerobic gram-positive organisms as a group and Candida spp. were isolated significantly more often in ESP anaerobic broths. Both systems detected 207 clinically significant bacteremic episodes and the ESP system alone detected 63, whereas the BACTEC NR660 system alone detected 32 (P < 0.05). Significantly more episodes of bacteremia caused by Staphylococcus epidermidis and anaerobes were detected by the ESP system. The differences in the numbers of organisms detected >6h earlier in ESP broths compared with BACTNEC NR660 broths were significant, as were earlier times to detection. Although the total number of organisms detected was not significantly different, the ESP system alone detected more organisms in a shorter time than did the BACTEC NR660 system alone. The continuous monitoring capability of the ESP system makes it an attractive alternative to the BACTEC NR660 system.