ASSESSMENT OF DIFCO ESP-384 BLOOD CULTURE SYSTEM BY TERMINAL SUBCULTURES - FAILURE TO DETECT CRYPTOCOCCUS-NEOFORMANS IN CLINICAL SPECIMENS

Terminal subcultures were performed on 1,162 5-day negative blood cult ure sets which had been monitored by the Difco ESP 384, a continuous-m onitor blood culture system. Of these, 16 (1.4%) had growth upon termi nal subculture. The isolates not detected by the Difco ESP 384 were Cr yptococcus neoformans (eight isolates), Candida albicans (one isolate) , Staphylococcus aureus (two isolates), coagulase-negative staphylococ cus (three isolates), Bacillus sp. (one isolate), and Corynebacterium sp. (one isolate). Acridine orange staining was performed on 200 rando mly selected negative blood culture sets from the study group. Of thes e, two sets were positive and grew out C. neoformans, as did the termi nal subculture. A review of patient's medical records indicated that m any of these false-negative isolates were clinically insignificant. Th e Difco ESP 384 failed to detect 1.4% of the isolates in this study, 5 0% of which were C. neoformans, indicating a deficiency in the detecti on mechanism of the system. Further studies demonstrated that while th ese isolates (C. neoformans) grew in the Difco media, the system did n ot detect this growth when the standard 5-day protocol was used.