Frequency and Predictors of Positive Follow-Up Blood Cultures in Patients with Streptococcal Bacteremia

Background Follow up blood cultures (FUBC) for streptococcal bacteremia are infrequently positive and may not provide sufficient clinical impact to justify the time and resources expended for their routine use. We aimed to evaluate the frequency and risk factors for positive FUBC in patients with streptococcal bacteremia, and to compare clinical outcomes among patients with and without positive FUBC. Methods We retrospectively reviewed hospitalized patients with streptococcal bacteremia from September 2023 to June 2024 within a multi-site health system. Patients 18 years or older with at least one positive blood culture for a Streptococcus species were included. Patients with polymicrobial bacteremia, those that died or discharged to hospice within 48 hours of their index culture, and Minnesota residents who declined research authorization were excluded. Results We included 454 patients, with 48 (10.6%) having positive FUBC. The rate of positivity ranged from 0% for S. pyogenes to 18.5% for S. anginosus. Endocarditis (22.9% vs 12.1%; P = 0.040) and osteomyelitis (16.7% vs 5.4%; P = 0.005) were more common in the positive FUBC group. Positive FUBC were associated with a higher incidence of infection relapse (8.5% vs 2.7%; P = 0.047) and longer duration of antibiotics (30 vs 16 days; P = 0.011), but no differences in mortality, length of stay, or infection-related readmission were observed. Conclusion Positive FUBC were infrequent for S. pyogenes, S. agalactiae, S. pneumoniae, and group C and G Streptococci. It may be reasonable to forego FUBC for these streptococcal species if endocarditis or osteomyelitis are not clinically suspected.