The effect of follow-up blood cultures on mortality and antibiotic use in gram-negative bloodstream infections

BACKGROUND: Gram-negative bloodstream infections (GN-BSIs) are a significant clinical challenge. The utility of follow-up blood cultures (FUBCs) in GN-BSIs and their impact on mortality and antibiotic consumption are areas of debate. This study aimed to evaluate the effect of FUBCs on mortality and antibiotic consumption in patients with GN-BSIs. METHODS: This single-center, retrospective study was conducted in aged > 18 years of patients with GN-BSIs. FUBC was defined as a blood culture performed 2–7 days after the first blood culture. Patients were grouped as FUBC and no FUBC and compared. A 1:1 match analysis was performed between the groups according to the SOFA score. The matched subgroup was compared for mortality risk factors with logistic regression models. The two groups were compared for the duration of effective antibiotic therapy and total antibiotic consumption (days of therapy per 1000 patient days (DOT/1000 PD)). RESULTS: FUBC was performed in 564 (69.4%) of 812 patients. Persistent, positive and negative FUBC rates were 7.9%, 14%, and 78%, respectively. The frequency of persistent GN-BSI in patients with appropriate antibiotic therapy was 3.9%. SOFA score (OR:1.33; 95% CI, 1.23–1.44), Charlson comorbidity index score (OR:1.18; 95% CI, 1.08–1.28), hospital-acquired infections (OR:1.93; 95% CI, 1.08–3.46) and carbapenem-resistant GN-BSI (OR: 2.92; 95% CI, 1.72–4.96) were independent risk factors for mortality. No relationship was found between FUBC and mortality (p > 0.05). Duration of effective antibiotic therapy (10(4–16) vs. 15(9–20), p < 0.001) and DOT/1000 PD (1609 (1000–2178) vs. 2000 (1294–2769), p < 0.001) were longer in the FUBC group. CONCLUSION: Routine FUBC should not be recommended because of the low prevalence of persistent infections in patients under appropriate antibiotic therapy and FUBC increases antibiotic consumption.