Specimen volume versus yield in the BACTEC blood culture system

Abstract

During a 24-month period, 5,625 blood culture specimens were collected at the Seattle Veterans Administration Medical Center in 20-ml volumes and divided into separate 10-ml aliquots. The two aliquots were processed as duplicate sets (set 1, set 2) by the BACTEC system (Johnston Laboratories, Inc., Towson, Md.). Specimens (5 ml) from each set were inoculated into aerobic (6B) and anaerobic (7C/7D) vials. A total of 434 significantly positive blood cultures were found. In 342 of these positive cultures, yielding 379 isolates (112 members of the family Enterobacteriaceae, 104 staphylococci, 87 streptococci, 27 anaerobes, 20 yeasts, 14 pseudomonads, and 15 miscellaneous organisms), there was adequate specimen volume to fill all four vials. The utilization of set 1 would have resulted only in the failure to detect 65 of 379 (17.2%) significant isolates, 52 of 342 (15.2%) positive cultures, and 20 of 198 (10.1%) bacteremic episodes. There were no significant differences in the recovery of individual species in sets 1 and 2. Although the range of isolates recovered by the aerobic and anaerobic vials of each set differed, the percent yield of total isolates was similar, indicating total isolate yield was predominantly a function of specimen volume. The addition of set 2 most dramatically increased the recovery of Escherichia coli (30%), yeasts (33%), and anaerobes (42%).

Correlation between time to positivity of blood cultures with clinical presentation and outcomes in patients with Klebsiella pneumoniae bacteraemia: prospective cohort study

“…The TTP of blood cultures can be influenced by several factors, including the volume of blood drawn, incubation conditions, time from specimen collection to receipt in the laboratory, the presence of growth inhibitors such as antibiotics, and the concentrations of the organism within the blood [22]. The volume of blood drawn was similar for all adult patients in this study, and the incubation conditions were stable because of the use of an automated system.…”

Effect of fluconazole prophylaxis on fungal blood cultures: an autopsy‐based study involving 720 patients with haematological malignancy

“…Conventional blood culture seems to be insensitive compared with the newly developed blood tests (Makimura et al , 1994; Obayashi et al , 1995). During the past two decades, there have been a number of changes in blood culture practices and systems (Auckenthaler et al , 1982; Plorde et al , 1985; Murray et al , 1991; Weinstein et al , 1991; Gutierrez et al , 1995; Pohlman et al , 1995a,b; Weinstein, 1996). However, the sensitivity of blood cultures has decreased since 1990.…”

“…While Aspergillus species are rarely cultured from blood samples (Duthie & Denning, 1995), detection of Candida species in the bloodstream is a key clinical laboratory strategy for establishing a diagnosis of invasive candidiasis. During the past two decades, there have been a number of changes in blood culture practices (Auckenthaler et al , 1982; Plorde et al , 1985; Weinstein, 1996). Manufacturers of blood culture systems and media have improved their products (Murray et al , 1991; Weinstein et al , 1991; Pohlman et al , 1995a,b), and there has been a marked trend towards the use of automated systems – most recently, continuous‐monitoring blood culture devices (Gutierrez et al , 1995).…”

Update on detection of bacteremia and fungemia.

“…Volume of blood cultured. Culturing adequate volumes of blood improves microbial recovery for both adult and pediatric patients (8,62,97,110,129,142,154,175). Indeed, the volume of blood cultured is the most important variable in optimizing microbial recovery for adult patients (142,209).…”