Clinical and microbiological characteristics of viridans group streptococcal bacteremia in pediatric and adolescent patients with cancer.

Viridans group streptococci (VGS) are an important cause of bacteremia inpediatric oncology patients and hematopoietic stem cell transplantation (HSCT) recipients, with the potential to viridans streptococcal shock syndrome (VSSS). Increasing β-lactam resistance has raised concerns about the adequacy of current empiric treatment strategies, which typically avoid routine glycopeptide use. We retrospectively analyzed 53 episodes of VGS bacteremia (VGSB) in 42 pediatric and adolescent patients who underwent chemotherapy or HSCT at Kobe Children's Hospital from May 2016 to August 2024. Clinical characteristics, antimicrobial susceptibility, inflammatory markers, and recurrence patterns were assessed. Acute myeloid leukemia (AML) accounted for 49% of episodes, and 60% occurred during cytarabine-containing chemotherapy. Seven patients experienced repeated episodes of VGSB-all with AML; among them, five developed cefepime resistance, and three showed a transition from susceptible to intermediate or resistant isolates during subsequent episodes. Cefepime susceptibility was 64%, whereas all isolates remained susceptible to vancomycin. Exposure to prophylactic antibiotics was significantly associated with the isolation of cefepime-intermediate or resistant strains (10/19 vs. 9/36, p = 0.03). Routine glycopeptide prophylaxis is not justified; however, our findings suggest that AML patients with recurrent VGSB or prior cefepime-nonsusceptible VGS may represent a high-risk subgroup for cefepime-nonsusceptible VGS infection. Further studies are needed to validate risk-adapted antimicrobial strategies in this population.