Retrospective evaluation of product blood cultures that tested on transplantation day in autologous peripheral stem cell transplantation

Microbiological screening for contamination is part of the haematopoietic stem cell collection and infusion procedure. Microbial contamination of hematopoietic stem cells (HSC) is rare but can lead to potentially lethal complications during transplantation. Bacterial contamination in the literature is reported in 2-7% of the cases. In the study, it was aimed to determine the microbial contamination rate of HSC products during the infusion phase and to evaluate the clinical course of patients transplanted with contaminating products at the same time. This study was conducted retrospectively in Uludağ University, School of Medicine, Heamatology Department, Bone Marrow Transplantation Unit. We included 228 patient who had been transplanted in our clinic with autologous heamatopoietic stem cells in between March 2009 and September 2017. Fifty four percent of the subjects were male and 46% were female; 65% were between 18 and 60 and 35% were older than 60 years of age. Diagnosis-wise distrubition of study subjects in descending order was; multiple myeloma 75%, hodgkin lymphoma 13%, non-hodgkin lymhoma 11% and plasma cell lymphoma 1%. Bacterial contamination was detected in 6 (2,7%) out of 216 samples, five of these contaminating agents were Staphylococcus epidermidis and one of them was Kocuria varians. Non of these 6 patients who were transplanted with contaminated stem cell product had presented with febrile neutropenia during transplantation procedure and control blood culture studies were not positive for contaminating agents nor any other pathogens. Furthermore non of these 6 patients were lost due to sepsis within the first 30 day period following transplantation. Also there was no significant difference in criteria related to fever and engraftment kinetics between patients transplanted with contaminated stem cell products and patients transplanted with non-contaminated stem cell products. In our study, the contamination of S. epidermidis may be the entryway - during catheter-based or urine sampling; Kocuria varians contamination is thought to be caused by external environment and skin flora. Most positive cultures in the literature are skin flora and contamination from external environment. In our study, the incidence of current contamination in peripheral stem cell apheresis procedures was found to be acceptable. It is important that the autologous peripheral blood stem cell is collected safely, that the hand hygiene should be protected during cryopreservation and dissolution, hand hygiene must be provided before and after the procedure, staff training and continuity of training should be ensured. Physicians and laboratory staff must make continuous efforts to minimize the risk of contamination of stem cell products. The reduction of contamination rates has a major role in the training and awareness of the apheresis team and the implementation of infection control measures. Key words: autologous peripheral stem cell, transplantation, contamination.