Risk factors for microbial contamination of peripheral blood stem cell products.

Background: Despite the well-known contamination rates and presence of microbial agents in stem cell products, the risk factors affecting microbial contamination have not been well described.

Study Design And Methods: In a 12-year period, we retrospectively reviewed culture results of peripheral blood stem cell products with the intent of identifying risk factors for microbial contamination.

Results: Microbial contamination was detected in 28 (5.7%) products of the postprocessing period and in 18 (3.66%) products of the postthawing period. Large-volume leukapheresis (LVL; odds ratio [OR], 5.85; 95% confidence interval [CI], 1.52-22.49; p = 0.01) and high numbers of stem cell culture sampling (OR, 1.4; 95% CI, 1.03-1.91; p = 0.03) were found to be risk factors for postprocessing bacterial contamination. The presence of postprocessing bacterial contamination was a risk factor for postthawing (OR, 28.89; 95% CI, 6.67-125.15; p < 0.001) and posttransplant (OR, 3.25; 95% CI, 1.24-8.50; p = 0.01) microbial growth. In transplants that were performed using contaminated products, the same pathogen was detected in 20% of patients and different pathogens were found in 35% of patients.

Conclusion: Cultures should be carefully monitored in LVL products and in samples with high numbers of cultures performed. Growth of different bacterial pathogens must be considered in transplants that are performed with contaminated products.