Can a stem cell product that has a positive culture for Staphylococcus epidermidis be reinfused in an autologous hematopoietic stem cell transplantation?

Reinfusion of Stem Cell Products with Positive Staphylococcus epidermidis Culture

Yes, stem cell products contaminated with Staphylococcus epidermidis can be safely reinfused in autologous HSCT with appropriate antibiotic prophylaxis, as clinical sequelae are rare and outcomes remain favorable.

Evidence Supporting Safe Reinfusion

Contamination Rates and Organisms

• Bacterial contamination of hematopoietic stem cell products occurs at a low frequency of approximately 1.0-1.3% across multiple large series 1, 2, 3
• Coagulase-negative Staphylococcus (including S. epidermidis) represents the predominant contaminant, accounting for 86.5% of all contaminated products 3
• These organisms are typically skin commensals introduced during collection or processing 1, 4

Clinical Outcomes with Contaminated Products

• Multiple studies demonstrate that infusion of S. epidermidis-contaminated grafts rarely results in unfavorable clinical outcomes 1, 4, 3
• In a 15-year series of 13 patients who received contaminated grafts, only one episode of S. epidermidis bacteremia possibly related to the contaminated product occurred (on day +5) 1
• A University of Minnesota study of 35 patients receiving contaminated products showed benign post-transplantation courses for all patients with coagulase-negative Staphylococcus contamination 2
• No microorganisms present in contaminated stem cell autografts were recovered in vivo during the post-transplantation period in one series, despite fever occurring in most patients 4

Management Algorithm

Antibiotic Prophylaxis Strategy

• Administer prophylactic antibiotics based on the organism identified from culture and antibiotic sensitivities 2, 3
• For S. epidermidis contamination, vancomycin is the empiric IV antibiotic of choice due to high prevalence of methicillin resistance in nosocomial strains 5
• Prophylactic antibiotics should be initiated before infusion of the contaminated product 2, 3

Monitoring Approach

• Close patient monitoring without specific pre-emptive antibiotics could be appropriate for Gram-positive skin contaminants to avoid antibiotic-associated adverse events 1
• However, given the immunocompromised state during HSCT, most centers favor prophylactic antibiotic coverage 2, 3, 6
• Obtain at least 2 sets of blood cultures if bacteremia is suspected post-infusion 5

Expected Clinical Course

• Febrile neutropenic episodes are common (occurring in 8 of 9 patients in one series), with median onset at day 4 (range 0-9 days) 6
• Admission lengths and time to engraftment remain within expected timeframes for autologous transplants 3
• No impact on neutrophil or platelet engraftment has been demonstrated 6

Critical Distinctions: When NOT to Reinfuse

Gram-Negative Contamination

• Exercise extreme caution with Gram-negative contaminated products 2
• One patient with Pseudomonas cepacia bacteremia ultimately died from complications after receiving a contaminated product 2
• Gram-negative organisms carry significantly higher risk than coagulase-negative Staphylococcus 2

Fungal Contamination

• Products contaminated with Aspergillus fumigatus should not be reinfused 4
• In one series, a concentrate contaminated with A. fumigatus was appropriately withheld, and the patient received only non-contaminated products 4

Common Pitfalls to Avoid

• Do not withhold S. epidermidis-contaminated products unnecessarily, as this may delay critical transplantation without clear benefit 1, 4, 3
• Do not initiate vancomycin for a single blood culture positive for coagulase-negative Staphylococcus if other concurrent cultures are negative, as this likely represents contamination rather than true infection 5
• Do not use vancomycin for routine prophylaxis of indwelling catheters, as this promotes vancomycin-resistant enterococci 5
• Avoid treating empirically without culture confirmation, as this contributes to antibiotic resistance 5

Strength of Evidence

The recommendation to proceed with reinfusion is based on multiple retrospective cohort studies spanning 15-25 years with consistent findings across institutions 1, 2, 4, 3, 6. While no randomized controlled trials exist (which would be unethical given the rarity of contamination and need for transplantation), the observational data strongly support safety when appropriate prophylaxis is used. The single caveat remains Gram-negative contamination, where heightened vigilance is warranted 2.