What is the role of bactericidal tests in the management of infective endocarditis (IE)?

Updated: Jan 03, 2019
  • Author: John L Brusch, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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Some clinicians obtain peak and trough blood samples during the course of antimicrobial therapy of IE in order to run serum bactericidal tests. These tests are performed by incubating serial 2-fold dilutions of serum that contains antimicrobials with an inoculum of 100,000 colony-forming units per milliliter of the target microorganism that has been previously isolated from the patient’s blood for 24-48 hours.

Peak antimicrobial concentrations that inhibit and kill the bacteria at a 1:32 or greater dilution in serum are a consistent predictor of a favorable clinical response. Antimicrobial dosages are adjusted to try to attain this goal. However, many clinicians feel that the serum bactericidal test does not have a reproducible result, and these clinicians rely on standardized tests of antimicrobial susceptibility (ie, MICs) and serum antimicrobial assays of peak and trough levels to determine whether sufficient amounts of antimicrobial agents are being administered. [83, 84, 85, 86, 87, 88]

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