Risk factors for positive follow-up blood cultures in Gram-negative bacteremia among immunocompromised patients with neutropenia.

Introduction: Gram-negative bacillary bloodstream infection (GN-BSI) is a frequent clinical challenge among immunocompromised hosts and is associated with a high mortality. The utility of follow-up blood cultures (FUBCs) for GN-BSI in this population, particularly in the setting of neutropenia, is poorly defined.

Methods: We conducted a single-center, retrospective cohort study between the period of July 2018 and April 2022 to investigate the utility of FUBCs and delineate risk factors for positive cultures among neutropenic patients with monomicrobial GN-BSI. Univariate logistic regression was performed to assess risk factors associated with positive FUBCs.

Results: Of 206 patients, 98% had FUBCs performed, and 9% were positive. Risk factors for positive FUBCs included multidrug-resistant GN infection (OR 3.26; 95% confidence interval [CI] 1.22-8.72) and vascular catheter source (OR 4.82; CI 1.76-13.17). Among patients lacking these risk factors, the prevalence of positive FUBCs was low (2.8%) and the negative predictive value was 92%. Those with positive and negative FUBCs had similar rates of all-cause mortality (16.7% vs. 16.6%; p = .942) and microbiologic relapse (11.1% vs. 6.0%; p = .401) within 90-days of treatment completion. However, positive FUBCs were associated with prolonged hospitalization and longer duration of antimicrobial therapy.

Conclusion: Positive FUBCs were infrequent in neutropenic patients with GN-BSI, and their occurrence did not significantly impact mortality or microbiologic relapse. Risk factors for positive FUBCs included multidrug resistant Gram-negative infection and vascular catheter source. Prospective studies will be necessary to elucidate the benefits and risks of FUBCs when managing GN-BSI in patients with underlying immune compromise.