Clinical Report: Bacterial Bloodstream Infections in Allogeneic Hematopoietic Cell Transplantation

Overview

Bacterial bloodstream infections (BSIs) remain a significant cause of morbidity and mortality in patients undergoing allogeneic hematopoietic cell transplantation (allo-HCT). These infections, including central line-associated bloodstream infections (CLABSIs) and mucosal barrier injury laboratory-confirmed bloodstream infections (MBI-LCBIs), contribute to prolonged hospitalization, intensive care needs, and increased non-relapse mortality.

Background

Allo-HCT is a curative treatment for various malignancies and immune deficiencies but is complicated by infectious risks, particularly bacterial BSIs. BSIs are classified as primary or secondary, with primary BSIs further divided into CLABSIs and MBI-LCBIs based on their origin. The presence of central venous catheters (CVCs) and mucosal barrier injury are key factors in BSI development. Despite advances in transplant strategies and supportive care, infection remains a leading cause of death post-transplant.

Data Highlights

Key Findings

• BSIs are the most common infectious complication following allo-HCT in both adults and children.
• Pre-engraftment BSIs are primarily associated with neutropenia, CVC presence, and severe mucositis.
• Post-engraftment BSIs are linked to acute and chronic graft-versus-host disease (GvHD), immunosuppression, and prior antibiotic exposure.
• CLABSIs and MBI-LCBIs are distinct entities; improved CVC care reduces CLABSI rates but not MBI-LCBIs.
• Risk factors for BSI include age >18 years, unrelated graft source, myeloablative conditioning, acute GvHD, mucositis, transplant-associated thrombotic microangiopathy, high-risk malignancy, and steroid use.
• Bacterial infections are more frequent after mismatched unrelated donor transplants compared to matched unrelated donor grafts.

Clinical Implications

Clinicians should recognize the high risk of BSIs in allo-HCT patients, particularly during the pre-engraftment period and in those with GvHD post-engraftment. Preventative strategies should focus on meticulous CVC care to reduce CLABSIs and address mucosal barrier injury to mitigate MBI-LCBIs. Awareness of patient- and transplant-related risk factors can guide targeted surveillance and antimicrobial stewardship to improve outcomes.

Conclusion

Bacterial bloodstream infections remain a persistent challenge in allo-HCT, significantly impacting patient morbidity and mortality. Differentiating infection types and understanding associated risk factors are essential for optimizing prevention and management strategies in this vulnerable population.

References

1. Mikulska et al. 2019 -- Incidence and Timing of BSIs in Allo-HCT
2. Kikuchi et al. 2020 -- Risk Factors and Outcomes of BSIs Post-Allo-HCT
3. Ballen et al. 2014 -- Infection Incidence in Acute Leukemia Patients Undergoing HCT
4. CDC NHSN 2013 -- Definitions for CLABSI and MBI-LCBI
5. IDSA 2018 -- Guidelines for Catheter-Related Bloodstream Infection Diagnosis