The Antibiotic Paradox in Allogeneic Stem Cell Transplantation

Overview

Antibiotic use in allogeneic stem cell transplantation (ASCT) is essential for managing infections but paradoxically contributes to intestinal dysbiosis, increasing the risk of severe acute graft-versus-host disease (GvHD). While early and prolonged antibiotics disrupt protective microbiota and worsen outcomes, targeted antibiotic use at GvHD onset may suppress bacterial translocation and mitigate disease severity.

Background

In ASCT, neutropenia and immunodeficiency necessitate prompt broad-spectrum antibiotic treatment to manage bloodstream infections (BSI), which occur in 13-30% of recipients and significantly increase mortality. Despite guidelines recommending antibiotic de-escalation during neutropenia, prolonged use is common. Advances in microbiota analysis reveal that early antibiotic exposure causes dysbiosis, favoring pathogenic bacteria and increasing inflammation, which correlates with worse transplant outcomes and higher acute GvHD risk. This creates a clinical paradox where antibiotics both harm and help depending on timing and context.

Data Highlights

Bloodstream infections affect 13-30% of ASCT recipients, markedly increasing mortality. A European survey found only 36% of centers discontinue antibiotics before neutrophil recovery. Early antibiotic use leads to loss of commensal bacteria and increased abundance of pathogens such as Enterococci, Klebsiella, E. coli, and Pseudomonas. Restrictive antibiotic protocols reduced early antibiotic use by 30% and delayed initiation by six days without compromising infection control.

Key Findings

• Early and prolonged antibiotic therapy induces intestinal dysbiosis, reducing protective commensal bacteria and increasing facultative and resistant pathogens.
• Dysbiosis correlates with increased bacterial translocation, inflammation, and higher risk of severe acute GI GvHD and mortality.
• Antibiotic treatment at GvHD onset can suppress bacterial translocation, reducing T cell activation and potentially mitigating GvHD severity.
• Antibiotics may blunt beneficial immune responses to checkpoint inhibitors and CAR T-cell therapies by disrupting microbiome diversity and metabolite production.
• Restrictive antibiotic protocols and improved diagnostics to differentiate infection from cytokine release syndrome can reduce unnecessary antibiotic exposure.
• Emerging molecular microbiota detection techniques may enhance infection diagnostics and guide antibiotic stewardship in ASCT.

Clinical Implications

Clinicians should balance the necessity of early antibiotic treatment for infection control with the risks of inducing dysbiosis and exacerbating GvHD. Adherence to antibiotic stewardship and de-escalation guidelines is critical to minimize prolonged exposure. Improved diagnostic tools to distinguish infectious fever from cytokine release syndrome can help restrict unnecessary antibiotic use, potentially improving transplant outcomes and preserving microbiome integrity.

Conclusion

The antibiotic paradox in ASCT underscores the dual role of antibiotics in both protecting against infection and contributing to adverse immune complications through microbiome disruption. Tailored antibiotic strategies that consider timing, duration, and patient context are essential to optimize outcomes.

References

1. Weber et al. -- Impact of Antibiotics on Microbiota and GvHD
2. Peled et al. -- Microbiota Diversity and Transplant Outcomes
3. van Bekkum et al. -- Germfree Models and GvHD Protection
4. Schwab et al. -- Bacterial Translocation in GvHD
5. Clinical Guidelines -- Antibiotic Use in Neutropenia