Background/Case Studies: Testing umbilical cord blood (UCB) for microbial contamination is one of the primary criteria for fulfilling the Association for the Advancement of Blood & Biotherapies (AABB) standards. Microbial contamination of cord blood (CB) is a significant risk affecting the final product's therapeutic value. Therefore, the cord blood bank continuously monitors and improves the workflow of the CB collection and processing procedures.
A recent study of significant importance delves into the impact of cryopreservation on the survival of microbes in CB units.
Study
Design/Methods: The investigation was conducted on 311 contaminated CB units collected between 1998 and 2008 when cryopreservation techniques were still evolving. The microbial contaminants in these CB samples before and after cryopreservation were compared.
Each contaminated sample was retrieved and thawed using a water bath at 37 °C with gentle shaking. 0.5 ml and 1 ml of the samples were then inoculated into BacT/ALERT ® BPA and BPN culture bottles for incubation for 14 days in the automatic blood culture system (Li et al., 2018). The positive bottles would be unloaded from the system with an alert signal and sent to a referral laboratory for microbial identification. The pre-freeze UBC samples were treated likewise before cryopreservation.
Results/Findings: The study found that Propionibacterium spp. (35.7%), Staphylococcus spp. (19.0%), and Escherichia coli (15.4%) were the most prevalent bacterial strains in the pre-freeze samples, among other 23 strains. Notably, 22.5% of the units had multiple contaminations before freezing, highlighting the need for further research and improved procedures to enhance the safety and efficacy of cord blood banking.
The study also revealed a 34.7% reduction in microbial contamination after prolonged cryopreservation. Escherichia coli (83.3%), Staphylococcus spp. (54.2%) and Enterococcus spp. (55.0%) had a higher detection rate in CB units that were originally contaminated with these microbes. However, Propionibacterium spp. (19.8%) and Lactobacillus spp. (36.4%) had a low recovery rate in the CB units contaminated with these microbes. Bacteroides spp., Peptostreptococcus spp., Eubacterium spp., Bifidobacterium spp. and Citrobacter spp. were not detectable in the retrospective CB units after prolonged cryopreservation.
Conclusions: The present study revealed Escherichia coli's resistance to prolonged cryopreservation. The relatively low recovery rate of Propionibacterium spp. and Lactobacillus spp. and the disappearance of Bacteroides spp., Peptostreptococcus spp., Eubacterium spp., Bifidobacterium spp., and Citrobacter spp. after cryopreservation underscore the critical need for further investigation.
