Impact on Reduction of Blood Culture Incubation Period from Five to Four Days from Large Tertitary Care Center

ABSTRACT

Background. Hospitals have been experiencing an increasing number of acutely ill patients as well as those requiring prolonged hospitalizations, further worsened by the COVID-19 pandemic. This has resulted in increased orders for blood cultures. Once collected, the culture bottles require an incubation period, typically 5 days. The BD BACTEC Fx, a blood culture incubation automated system, holds blood culture bottles until growth is demonstrated or for 5 days, whichever occurs first. New bottles are placed in the apparatus along with older bottles awaiting growth. Capacity is reached when the machine cannot accommodate new bottles due to limited space.When this occurs,manual plating of blood cultures on agar plates is required. Manual plating adds additional responsibility to already overwhelmed microbiology labs. Methods. Following the institutional review board (IRB) approval, data were collected retrospectively at a 765-bed tertiary care center. Data was obtained from positive blood cultures from July 2017 to June 2020. We stratified positive blood cultures based on the day of positivity, from day one to day five. The charts were reviewed for positive blood culture results on day four and day five to evaluate for clinical significance. Clinical significance was determined by an Infectious Disease subspecialty team. Blood culture bottles that were positive on day 4 and day 5 in 1 bottle out of 2 bottles with coagulase-negative species of Staphylococcus, Corynebacterium spp, or Propionibacterium acnes were considered a contaminant and did not warrant further chart review. Results. On a retrospective review of data from July 2017 to June 2020, the total number of blood cultures obtained was 120,320. Among them, 7,558 blood cultures were positive. 94% were positive on day 1, 4% positive on day 2, 2% positive on day 3, 1% positive on day 4 and < 1% positive on day 5. Positive blood cultures on day 5 did not have any clinical significance, according to the chart review. Conclusion. Our study demonstrated that four days of incubation is sufficient for the BD BACTEC Fx automated blood culture incubation system without compromising clinical significance. Implementation of a 4-day incubation period will help with reducing saturation of slots and will improve readiness to accommodate more blood culture bottles.