Ramirez-Arcos, Sandra - Research and Publications

Bacterial contamination of fresh blood components is the most prevalent transfusion-associated infectious risk, and platelet concentrates (PCs) are the blood product most likely to be infected. Dr. Ramirez’ applied research projects further our understanding of contamination of fresh blood components and stem cell products and help develop better methodologies for bacterial detection.

Dr. Ramirez’ research on detection of bacterial growth in blood and stem cell products contributes to the distribution of safer blood products for Canadian patients.

Dr. Ramirez' team regularly tests the methods used for routine screening of PCs and stem cell components for contamination at Canadian Blood Services and works with industry partners to evaluate new technologies for the detection of bacterial contamination. More recently, her team validated a screening method for bacterial contamination in cord blood units. Dr. Ramirez and her research group have also investigated bacterial contamination of red blood cell (RBC) components, an issue despite their storage at 4 °C. They have shown that multiple exposures of RBC units to room temperature for up to one hour do not adversely affect the safety of RBCs. This study provided evidence to the Canadian Standards Association to change the maximum time limit of uncontrolled temperature exposure from 30 minutes to 60 minutes, a decision that will reduce wastage of RBC units without compromising safety or efficacy of the product. Dr. Ramirez’ group is regularly involved in investigations of adverse reactions due to transfusion of contaminated blood components. Her team has developed and patented a rapid, highly sensitive and specific assay to discriminate Staphylococcus epidermidis from other staphylococcal species in PCs, an important advance as PCs are at particular risk of being contaminated with S. epidermidis, a skin contaminant. Dr. Ramirez’ team is participating in a World Health Organization-endorsed international study to develop a panel of bacterial strains suitable for validation and comparison assessments.

Current research in Dr. Ramirez' lab is focused on:

1. Developing a method to detect bacteria in cord blood units that contain antibiotics.
2. Assessing bacterial survival during buffy coat platelet production and storage.
3. Evaluating the effectiveness of pathogen reduction technologies on biofilm-forming bacteria.

Dr. Ramirez' team has developed extensive expertise around bacteria forming surface-attached aggregates known as biofilms. The formation of such biofilms is associated with increased pathogenicity and might explain instances of missed bacterial detection in blood components.

Biofilm formation is a serious hurdle for the detection and elimination of bacterial contamination of blood products. Dr. Ramirez’ work informs efforts to prevent contamination from these bacteria and improve their detection, at every step from skin disinfection before donation to testing our final products.

Dr. Ramirez has shown that bacteria form surface-attached communities of cells known as biofilms during platelet storage and that these biofilms may not be detected during screening, as biofilms adhere to the inner surfaces of the platelet bags and/or to platelets, which may result in a decreased number of cells in suspension available for screening and enhanced pathogenicity. Dr. Ramirez’ research seeks to understand factors influencing biofilm formation. Dr. Ramirez' team screened skin flora bacteria isolated from contaminated PCs in Canada for their biofilm-forming ability and surprisingly found that some of these presumable harmless bacteria display a virulent phenotype. Importantly, they have recently shown that these biofilm‐forming skin microflora bacteria are resistant to the bactericidal action of disinfectants used during blood donation. Her group has also shown that anaerobic bacteria cannot replicate during platelet storage, but can survive in the presence of oxygen, likely as a result of the formation of biofilms. Investigation of preventive measures to control biofilm formation in PCs has resulted in the development of a patent showing that polyethylene glycol-modification of the platelet surface results in significant reduction of bacterial biofilm formation. Furthermore, Dr. Ramirez’ team has reported that biofilm formation is reduced in PCs suspended in platelet additive solutions compared to plasma-suspended PCs.

Current research in Dr. Ramirez' lab is focused on:

1. Determine the contribution of the platelet storage environment and plastic material of platelet containers to bacterial biofilm formation.
2. Assess biofilm resistance to synthetic and platelet-derived antimicrobial peptides and natural oils.
3. Conduct comparative studies of the expression, at the mRNA level, of S. epidermidis genes when grown in media and PCs.