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

Abstract Background Follow-up blood cultures (FUBCs) 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 of and risk factors for positive FUBCs in patients with streptococcal bacteremia and to compare clinical outcomes among patients with or without positive FUBCs. Methods We retrospectively reviewed hospitalized patients with streptococcal bacteremia from September 2023 to June 2024 within a multisite health system. Patients ≥18 years old with ≥1 positive blood culture for a Streptococcus species were included. Patients with polymicrobial bacteremia, those who died or were 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 FUBCs. The rate of positivity ranged from 0% for Streptococcus pyogenes to 18.5% for Streptococcus anginosus. Endocarditis and osteomyelitis were more common in the positive than in the negative FUBC group (22.9% vs 12.1%, respectively, for endocarditis [P = .04] and 16.7% vs 5.4% [P = .005] for osteomyelitis). Positive FUBCs were associated with a higher incidence of infection relapse (8.5% vs 2.7%; P = .047) and longer duration of antibiotics (30 vs 16 days; P = .01), but no differences in mortality rate, length of stay, or infection-related readmission were observed. Conclusions Positive FUBCs were infrequent for S pyogenes, Streptococcus agalactiae, Streptococcus 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.