Is the Volume of Blood Cultured Still a Significant Factor in the Diagnosis of Bloodstream Infections?

Abstract

"The higher the volume of blood cultured the higher the yield of blood cultures" has been a well-accepted dictum since J. A. Washington II performed his classic work. This rule has not been questioned in the era of highly automated blood culture machines, nor has it been correlated with clinical variables. Our objective in this study was to complete a prospective analysis of the relationship between blood volume, the yield of blood cultures, and the severity of clinical conditions in adult patients with suspected bloodstream infections (BSI). During a 6-month period, random samples of blood cultures were weighed to determine the volume of injected blood (weight/density). Overall, 298 patients with significant BSI and 303 patients with sepsis and negative blood cultures were studied. The mean volume of blood cultured in patients with BSI (30.03 ؎ 14.96 ml [mean ؎ standard deviation]) was lower than in patients without BSI (32.98 ؎ 15.22 ml [P ‫؍‬ 0.017]), and more episodes of bacteremia were detected with <20 ml (58.9%) than with >40 ml (40.2%) of blood cultured (P ‫؍‬ 0.022). When patients were stratified according to the severity of their underlying condition, patients with BSI had higher APACHE II scores, and higher APACHE II scores were related to lower sample volumes (P < 0.001). A multivariate analysis showed that in the group of patients with APACHE II scores of >18, higher volumes yielded higher rates of bacteremia (odds ratio, 1.04 per ml of blood; 95% confidence interval, 1.001 to 1.08). We conclude that the higher yield of blood cultures inoculated with lower volumes of blood reflects the conditions of the population cultured. Washington's dictum holds true today in the era of automated blood culture machines.According to the classic literature, the volume of blood per culture is the single most important variable in recovering microorganisms from patients with sepsis. The higher the blood volume cultured, the higher the rate of detection of bloodstream infections (BSI) (1, 5-7, 9, 12, 15, 18, 20, 21). However, reports regarding the requirements for blood volume with today's automated and continuous-monitoring blood culture systems are scarce (12,15,22,24). In a previous study, we noted that blood cultures inoculated with lower volumes had a higher yield of detection of BSI at our institution (17).The aim of the present study was to reassess the importance of blood volume in the yield of blood cultures after the introduction of automated systems with continuous agitation and to correlate the findings with clinical variables. MATERIALS AND METHODSOur institution is a general teaching hospital with 1,750 beds serving a mainly urban population of 650,000. We have medical and surgical specialties as well as large psychiatric, obstetric, and pediatric facilities. We have very active bone marrow and solid organ transplantation programs and serve as a referral institution.Study period and patient selection. The study was carried out during a period of 6 months. We randomly selected one of every two episodes o...

Correlation between inoculum volume, positivity rates and microorganisms isolated from blood cultures

“…In this study, the overall incidence of positive results of 9.2% was lower than the internationally reported rate of 21.5-24.5% (Gonsalves et al, 2009;Bouza et al, 2007). A probable explanation could be due to the increased risk of mortality in patients with bacteraemia, in which there is generally a lower threshold for drawing blood culture samples, which increased our denominator (Bates and Goldman, 1991).…”

“…Each inoculated bottle was weighed to two decimal places using a digital balance. The volume of blood in each bottle was calculated by subtracting the weight of the uninoculated bottle from the weight of inoculated bottle as described previously (Bouza et al, 2007), and the density of blood was assumed to be 1 (Lingwood et al, 2006). All bottles were incubated at 35°C in asemi-automated BACTEC system (BD Diagnostics) and monitored for a positive signal over a five-day period.…”

Bacteraemia coincides with low citrulline concentrations after high-dose melphalan in autologous HSCT recipients

“…This is most likely a direct consequence of giving ciprofloxacin as prophylaxis, which effectively prevents bacteraemia due to Gram-negative bacilli, while giving selective advantage to the less susceptible Grampositive bacteria. 18 The blood cultures of 5 of the 10 patients with bacteraemia yielded two bacterial species that might simply reflect greater sampling efficiency, as we obtained a total of 70 ml of blood for blood cultures, which is more than others report 19 Viridans streptococci are primarily oral commensal flora; however, molecular analysis of the microbiota in the stomach shows that these bacteria can be found in large numbers along with Helicobacter pylori. 20 In children treated for AML, there was an association between the presence of gastrointestinal toxicity and the development of viridans group streptococcal bacteraemia.…”

Usefulness of routine pairing of anaerobic with aerobic blood culture bottles and decision making on antimicrobial therapy

“…Some previous studies focused on the potential benefit of keeping anaerobic bottle on board though anaerobe recoveries were not high, anticipating the growth of facultative anaerobes like staphylococci, streptococci, and some members of the family Enterobacteriaceae. However, it was observed that the amount of blood injected per bottle was associated with a better growth yield, this argues against the routine anaerobic bottles use, which is if the blood volume was saved for aerobic bottles [14,15]. Only one patient in the 4 discordant paired bottles grew an organism that called for intervention by a clinician.…”