Follow-up Blood Cultures in Gram-Negative Bacteremia: Are They Needed?

Bloodstream infections remain a major cause of morbidity and mortality. Gram-negative bacilli (GNB) bacteremia is typically transient and usually resolves rapidly after the initiation of appropriate antibiotic therapy and source control. The optimal duration of treatment and utility of follow-up blood cultures (FUBC) have not been studied in detail. Currently, the management of gram-negative bacteremia is determined by clinical judgment. To investigate the value of repeat blood cultures, we analyzed 500 episodes of bacteremia to determine frequency of FUBC and identify risk factors for persistent bacteremia.

Of 500 episodes of bacteremia, we retrospectively analyzed 383 (77%) that had at least 1 FUBC. We sought information regarding presumed source of bacteremia, antibiotic status at the time of FUBC, antibiotic susceptibility, presence of fever, comorbidities (intravenous central lines, urinary catheters, diabetes mellitus, AIDS, end-stage renal disease, and cirrhosis), need for intensive care, and mortality.

Antibiotic use did not affect the rate of positivity of FUBC, unless bacteria were not sensitive to empiric antibiotic. Fever on the day of FUBC was associated with higher rates of positive FUBC for gram-positive cocci (GPC) but not GNB. Mortality and care in the intensive care unit were not associated with positive FUBC. Seventeen FUBC and 5 FUBC were drawn for GNB and GPC to yield 1 positive result.

FUBC added little value in the management of GNB bacteremia. Unrestrained use of blood cultures has serious implications for patients including increased healthcare costs, longer hospital stays, unnecessary consultations, and inappropriate use of antibiotics.