[ID] Repeat Blood culture?

[Category] Topic; 1. Workup; 2. Management; 3. Tip and Teaching point; 4. References;

[ID] Culture positive

1. n/a

2. If we identify the source of infection or suspicious of source, we will treat empirically.

3. Repeat blood culture daily from the day of positive until it is clearing.
    Or
    Resend blood culture when pt. shows breakthrough fever or any other sign of infection.

=> Gram(+) MRSA; IDSA recommends cultures 2-4 days after index positie culture 
     Candidemia: daily blood culture
     Gram(-) or Str.: low yield. 

4. Reference as below. 

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Readings.

1. [Uptodate] Blood culture for the detection of bacteremia.

Blood cultures for the detection of bacteremia

●Blood cultures should be obtained (prior to initiation of antimicrobial therapy) for any patient in whom there is suspicion of bacteremia, including hospitalized patients and selected outpatients with fever and leukocytosis or leukopenia. However, a normal white blood count does not rule out bacteremia. Circumstances in which blood cultures are especially important include sepsis, meningitis, osteomyelitis, arthritis, endocarditis, peritonitis, pneumonia, and fever of unknown origin. (See 'Indications for cultures' above.)

●Prior to initiation of antimicrobial therapy in adults, at least two, preferably three, sets of blood cultures taken from separate venipuncture sites should be obtained. The technique, number of cultures, and volume of blood are more important factors for detection of bacteremia than timing of culture collection. (See 'Method for obtaining cultures'above.)

●Important measures to reduce contamination include effective disinfection of the venipuncture site and avoiding blood culture collection through existing intravenous lines. The appropriate volume for adults is a minimum of 10 mL (and preferably 20 mL) of blood; the appropriate volumes for children are summarized in the table (table 1). (See 'Technique' above and 'Volume of blood' above and 'Timing' above.)

●There are two clinical patterns of bacteremia: intermittent and continuous. Intermittent bacteremia implies that bacteria are present in the blood for periods of time followed by nonbacteremic periods; this is the most common pattern. Continuous bacteremia usually reflects a persistent endovascular infection such as endocarditis. (See 'Types of bacteremia' above.)

●Organisms for which it can be difficult to distinguish between pathogenicity and contamination include Cutibacterium(formerly Propionibacterium) acnes, Corynebacterium species, Bacillus species, and coagulase-negative staphylococci; the likelihood of pathogenicity is increased if the organism is observed in multiple blood cultures obtained from separate venipunctures. (See 'Contamination' above.)

2. [BMC Infect Dis]  Sending repeat cultures: is there a role in the management of bacteremic episodes? (SCRIBE study) J. Brad Wiggers, Wei Xiong, and Nick Daneman

LINK: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4906775/

Abstract

Background

In the management of bacteremia, positive repeat blood cultures (persistent bacteremia) are associated with increased mortality. However, blood cultures are costly and it is likely unnecessary to repeat them for many patients. We assessed predictors of persistent bacteremia that should prompt repeat blood cultures.

Methods

We conducted a retrospective cohort study of bacteremias at an academic hospital from April 2010 to June 2014. We examined variables associated with patients undergoing repeat blood cultures, and with repeat cultures being positive. A nested case control analysis was performed on a subset of patients with repeat cultures.

Results

Among 1801 index bacteremias, repeat cultures were drawn for 701 patients (38.9 %), and 118 persistent bacteremias (6.6 %) were detected. Endovascular source (adjusted odds ratio [aOR], 7.66; 95 % confidence interval [CI], 2.30-25.48), epidural source (aOR, 26.99; 95 % CI, 1.91-391.08), and Staphylococcus aureus bacteremia (aOR, 4.49; 95 % CI, 1.88-10.73) were independently associated with persistent bacteremia. Escherichia coli (5.1 %, P = 0.006), viridans group (1.7 %, P = 0.035) and β-hemolytic streptococci (0 %, P = 0.028) were associated with a lower likelihood of persistent bacteremia. Patients with persistent bacteremia were less likely to have achieved source control within 48 h of the index event (29.7 % vs 52.5 %, P < .001), but after variable reduction, source control was not retained in the final multivariable model.

Conclusions

Patients with S. aureus bacteremia or endovascular infection are at risk of persistent bacteremia. Achieving source control within 48 h of the index bacteremia may help clear the infection. Repeat cultures after 48 h are low yield for most Gram-negative and streptococcal bacteremias.

Keywords: Bacteremia, Bloodstream infection, Epidemiology, Blood cultures, Gram-positive bacteria, Gram-negative bacteria

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3.  ref. Repeating blood cultures after initial bacteremia: When and how often? Cleveland Clinic Journal of Medicine. 2019 February;86(2):89-92

FREQUENCY OF REPEAT BLOOD CULTURES

There are no evidence-based guidelines for the frequency of repeating cultures. The Infectious Diseases Society of America recommends repeating blood cultures 2 to 4 days after the index positive culture in the case of multidrug-resistant S aureus bacteremia, and every day or every other day for candidemia.6,7,9

A study evaluating the practice patterns of repeating cultures after an initial bacteremia showed that 34.7% were done within 24 hours and 44.7% were done in 2 to 4 days.1 There is no evidence that repeating blood cultures daily is necessary in these patients. As a general rule, it should be done 48 to 72 hours after a positive culture.