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Antibiotic Use in Sepsis

　　Jonathan Cohen, MD,[7] then spoke about antibiotic choice in sepsis. It might seem appropriate to have a critical pathway that mandated the same antibiotic selection for every patient who was septic. This monolithic approach would be consistent, but would not likely maximize outcome. The appropriate choice of antibiotic for an individual patient may increase efficacy by increasing the likelihood that an active drug is chosen. Knowledge of prior antibiotics, or prior colonizing or infecting organisms, would influence drug selection. The appropriate choice of antibiotic might also decrease toxicity by avoiding drugs that might exacerbate underlying organ dysfunction. In a study published in 1980, Kreger and coworkers[8] demonstrated that the choice of antibiotic therapy that is active against the causative organism improves patient outcome compared with patients who received drugs that were not active against the offending pathogen, as clinicians might intuitively suspect. More recent studies have confirmed Kreger's results.
　　Dr. Cohen described the utility of a test that has not been used for many years in understanding outcome. Laboratory tests can measure the ability of antibiotic-containing serum to kill the patient's pathogen. The bacteridical titer has been defined as the concentration of serum that kills 95% of an inoculum. These titers assess both the effect of host factors and the effect of the antibiotic. Patients with higher peak titers have better outcomes than patients who have lower peak titers. However, this assay is not terribly practical because of wide variability in laboratory techniques and resulting nonreproducibility of results. More recently, automated blood culture systems measure the hours until growth of bacteria is recognized. This time is an approximation of bactericidal activity. (This is also a surrogate marker for the quantity of circulating bacteria, which is a reciprocal concept.) The shorter the time to culture positivity, the worse the patient's prognosis. Increasing the amount of antibiotic in each specimen (ie, higher serum antibiotic levels) also leads to longer time to culture positivity.