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Published on: June 8, 2022
The peptidoglycan and biofilm matrix of Staphylococcus epidermidis undergo structural changes when exposed to human
Maria Loza-Correa1,2, Juan A Ayala3, Iris Perelman1
1Centre for Innovation, Canadian Blood Services, Ottawa, Canada.
Abstract:
Staphylococcus epidermidis is a bacterium frequently isolated from contaminated platelet concentrates (PCs), a blood product used to treat bleeding disorders in transfusion patients. PCs offer an accidental niche for colonization of S. epidermidis by forming biofilms and thus avoiding clearance by immune factors present in this milieu. Using biochemical and microscopy techniques, we investigated the structural changes of the peptidoglycan (PG) and the biofilm matrix of S. epidermidis biofilms formed in whole-blood derived PCs compared to biofilms grown in glucose-supplemented trypticase soy broth (TSBg). Both, the PG and the biofilm matrix are primary mechanisms of defense against environmental stress. Here we show that in PCs, the S. epidermidis biofilm matrix is mainly of a proteinaceous nature with extracellular DNA, in contrast to the predominant polysaccharide nature of the biofilm matrix formed in TSBg cultures. PG profile studies demonstrated that the PG of biofilm cells remodels during PC storage displaying fewer muropeptides variants than those observed in TSBg. The PG muropeptides contain two chemical modifications (amidation and O-acetylation) previously associated with resistance to antimicrobial agents by other staphylococci. Our study highlights two key structural features of S. epidermidis that are remodeled when exposed to human platelets and could be used as targets to reduce septic transfusions events.
Insights
Staphylococcus epidermidis biofilms in platelet concentrates (PCs) have a protein-rich matrix and altered peptidoglycan (PG). These changes, compared to standard lab growth, may impact bacterial defense and could be targets to prevent transfusion-associated sepsis.
Area of Science:
- Microbiology
- Biochemistry
- Transfusion Medicine
Background:
- Staphylococcus epidermidis frequently contaminates platelet concentrates (PCs).
- PCs provide a niche for S. epidermidis biofilms, evading immune clearance.
- Biofilms utilize peptidoglycan (PG) and matrix components for defense.
Purpose of the Study:
- To investigate structural changes in S. epidermidis biofilms grown in PCs versus laboratory media.
- To compare the biofilm matrix composition and PG structure under different conditions.
Main Methods:
- Biochemical analysis of biofilm matrix and PG.
- Microscopy techniques to visualize structural changes.
- Comparison of biofilms grown in whole-blood derived PCs and glucose-supplemented trypticase soy broth (TSBg).
Main Results:
- S. epidermidis biofilms in PCs feature a protein and extracellular DNA matrix, unlike the polysaccharide matrix in TSBg.
- PG remodeling in PCs leads to fewer muropeptide variants compared to TSBg.
- PG modifications (amidation, O-acetylation) observed in PC biofilms are linked to antimicrobial resistance.
Conclusions:
- S. epidermidis structurally adapts its biofilm matrix and PG in response to human platelet environments.
- These adaptive changes may influence bacterial survival and virulence in PCs.
- Targeting these remodeled structural features could mitigate transfusion-related sepsis events.
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