# Formation of Single-Species and Multispecies Biofilm by Isolates from Septic Transfusion Reactions in Platelet Bag Model

## TL;DR

This study investigates how bacteria from septic transfusion reactions form biofilms in platelet units, which may help them evade detection and control methods.

## Contribution

The study introduces a new plate-based method to evaluate biofilm formation by bacteria isolated from septic transfusion reactions.

## Key findings

- Most bacterial combinations produced more biofilm than single-species biofilms.
- Combinations involving Leclercia adecarboxylata showed increased biofilm production and bacterial adherence.
- Biofilms formed by transfusion-relevant bacteria may impact bacterial risk control strategies.

## Abstract

During 2018–2021, eight septic transfusion reactions occurred from transfusion of platelet units contaminated with Acinetobacter spp., Staphylococcus saprophyticus, Leclercia adecarboxylata, or a combination of those environmental organisms. Whether biofilm formation contributed to evasion of bacterial risk mitigations, including bacterial culture, point-of-care testing, or pathogen-reduction technology, is unclear. We designed a 12-well plate-based method to evaluate environmental determinants of single-species and multispecies biofilm formation in platelets. We evaluated bacteria isolated from septic transfusion reactions for biofilm formation by using crystal violet staining and enumeration of adherent bacteria. Most combinations of bacteria had enhanced biofilm production compared with single bacteria. Combinations involving L. adecarboxylata had increased crystal violet biofilm production and adherent bacteria. This study demonstrates that transfusion-relevant bacteria can produce biofilms well together. More work is needed to clarify the effect of biofilms on platelet bacterial risk control strategies, but US Food and Drug Administration–recommended strategies remain acceptable.