Clinical Impact of Preincubation of Blood Cultures at 37°C

Abstract

The effect of immediate incubation of blood cultures at 37°C on the turnaround time and the impact of Gram stain results on antimicrobial management were investigated. During a 6-month period, blood cultures collected at the emergency department outside laboratory operating hours were preincubated at 37°C until transportation to the laboratory. Upon the arrival of blood cultures at the laboratory, Gram stains and subcultures were made from all bottles prior to further incubation in the automated system (Bactec 9240). Data from 1 year earlier, when all blood cultures were stored at room temperature, were used for comparison. In the study period, 79 episodes of bacteremia were detected for 75 patients, compared to 70 episodes for 67 patients in the control period. Preincubation of blood cultures at 37°C resulted in a 15-h reduction in the median time to reporting of Gram stain results, from 34 to 19 h (P, <0.001). With preincubation, 3 episodes (4%) of bacteremia were not detected by the Bactec 9240 system. Based on the reporting of the Gram stain results, appropriate antimicrobial therapy was initiated for 12% of all patients with positive blood cultures, while for 24% the therapy was streamlined. Thus, immediate incubation of blood cultures reduced the time to reporting of Gram stain results. However, not all episodes of bacteremia were detected by the Bactec 9240 system after preincubation at 37°C. Blood culture results contributed importantly to appropriate antimicrobial management.Appropriate antibiotic therapy initiated in a timely manner has been shown to reduce mortality in patients with bloodstream infections (5-7). Therefore, if a bloodstream infection is suspected, blood should be collected for culture as soon as possible, preferably before antimicrobial therapy is initiated. Ideally, blood culture results lead either to the streamlining of broad-spectrum empirical therapy or to the initiation of appropriate therapy (3). Blood culture results may also help to confirm or identify the site of infection.To optimize the clinical use of blood culture results, the interval between the collection of blood and the entry of the bottles into an automated blood culture system should be kept to a minimum. However, many microbiology laboratories do not provide 24-h service, and cultures obtained outside operating hours are often stored at room temperature before entry into the system. Aside from laboratory operating hours, the use of satellite laboratories referring blood cultures to their reference laboratory can cause a significant delay in bottle entry into the system. This delayed entry has been shown to result in increased times to detection of bacteremia and longer hospital stays (1, 9).To overcome this problem, an automated blood culture system can be placed outside the laboratory, and blood cultures may be entered by health care workers. Such an approach resulted in a 10-h reduction in the interval between blood culture collection and growth detection (6). Since it is not always feasible to place a monitorin...

Impact of Pre-Analytical Time on the Recovery of Pathogens from Blood Cultures: Results from a Large Retrospective Survey

“…In clinical operative settings some previous studies on pre-analytical conditions and length and their effects on the time occurring for a microbiological diagnosis have been performed [14–15, 33–35]. None of these investigations looked at microorganism recovery or at changes in the probability of positive results.…”

Current approaches to the diagnosis of bacterial and fungal bloodstream infections in the intensive care unit

“…These delays can occur both at the patient's bedside and in the laboratory. Kerremans et al [28, 29] and van der Velden et al [30] demonstrated in a series of elegant studies that incubation delays for almost half of all blood cultures exceeded 4 hours (including median transport times of 3.9h and 16.0h for specimens from the ICU and Emergency Department, respectively), preincubation at the collection site significantly reduced the time to detection of positive cultures, and this resulted in more rapid adjustment of antibiotic therapy. Although blood culture instruments are rarely used outside the clinical lab, the installation of such instruments proximate to ICUs should be considered in high volume settings where transport delays are likely.…”

Effects of Preincubating Blood Culture Bottles at 37℃ during the Night Shift and of Collected Blood Volume on Time to Detection and Days to Final Report

“…considered to avoid false negatives [7], although this procedure requires significant laboratory resources. In a previous study [6], Although this study has several limitations, we may conclude that collecting adequate blood volume is critical to reduce TTD and that there is the significant benefit of receiving earlier final reports when preincubating the bottles at 37 o C when delayed entry is inevitable.…”