By Stan Deresinski, MD, FACP, FIDSA

Clinical Professor of Medicine, Stanford University

SYNOPSIS: A study of significantly immunocompromised patients with gram-negative bacteremia concluded that the routine use of follow-up blood cultures to document clearance is not warranted.

SOURCE: Groft L, Mease J, Bork J, et al. Follow-up blood culture practices for gram-negative bloodstream infections in immunocompromised hosts at a large academic medical center. Abstract 62. IDWeek 2021.

Although follow-up blood cultures (FUBC) to evaluate the microbiologic effectiveness of antimicrobial therapy are recommended in patients with bloodstream infection with either Staphylococcus aureus or Candida species, their usefulness in patients with gram-negative bacteremia has been questioned.1 Groft and colleagues took this question a step further by examining the yield of FUBC obtained 24 hours to seven days after the initial positive culture in a particularly at-risk subset of patients with gram-negative bacteremia those with significant immunocompromise. Patients included had an active malignancy, solid organ or hematopoietic cell transplant, or absolute neutrophil count < 1,000/mm3.

FUBC were obtained for 129 (88.4%) of 146 patients. One-third of the infections were caused by Escherichia coli, 23.3% by Pseudomonas aeruginosa, and 21.9% by Klebsiella pneumoniae.

Only 17.8% of patients had a urinary tract source, while approximately one-half had a gastrointestinal or intraabdominal source, and one-tenth arose from a central venous access device. FUBC was positive with the same organism as the index isolate in only two cases (1.4%) and both were febrile at the time. Thus, the number of patients needed to test to detect one case of persistent bacteremia was 71.4.

In contrast, some authors have concluded that FUBC are of value in patients with gram-negative bacteremia.

Canzoneri and colleagues reported their retrospective experience with FUBC in 2017.1 Their positivity rate on repeat culture was higher than that found by Croft et al, with eight (5.7%) of 140 patients having positive repeats. None of the eight died. Furthermore, six of the eight were febrile at the time the repeat culture was obtained. They concluded by stating caution against the routine practice of repeating blood cultures in patients with gram-negative bacteremia.

On the basis of a literature review, Cogliati Dezza concluded that FUBC could be of value in critically ill patients, those with endovascular and/or non-eradicable source of infection, isolation of a multidrug-resistant pathogen, end-stage renal disease, and immunodeficiencies, and that in such circumstances, the result could alter management.2

However, the study by Croft et al strongly supports the conclusion that routine FUBC, in the absence of additional specific risk factors, is not warranted in patients with gram-negative bacteremia even in those with severe immunocompromise and should be performed only in selected patients with specific indications. 

REFERENCES

  1. Canzoneri CN, Akhavan BJ, Tosur Z, et al, Follow-up blood cultures in gram-negative bacteremia: Are they needed? Clin Infect Dis 2017;65:1776-1779.
  2. Cogliati Dezza FC, Curtolo A, Volpicelli L, et al. Are follow-up blood cultures useful in the antimicrobial management of gram negative bacteremia? A reappraisal of their role based on current knowledge. Antibiotics (Basel) 2020;9:895.