Induction of Candida albicans biofilm formation on silver-coated vascular grafts
Ina Tammer1, Julia Reuner, Roland Hartig
1Institute of Medical Microbiology, Otto von Guericke University, 39120 Magdeburg, Germany.
Objectives:
Silver exhibits excellent antimicrobial properties and is used to protect medical devices from microbial colonization. Because few data are available on the influence of silver coating of vascular prostheses on Candida biofilm formation, this study aimed to investigate the effect of silver on yeast biofilm formation in an in vitro model.
Methods:
Prosthesis material was co-cultivated with two different strains of Candida albicans and the effect of silver on attachment and the growth of biofilms was monitored by microscopy and by quantification of cfu and mitochondrial dehydrogenase activity.
Results:
Silver collagen-coated vascular prostheses significantly reduced C. albicans biofilm formation in serum-free medium. Paradoxically, in the presence of 50% serum, silver increased the growth of biofilms on silver-containing prostheses 2- to 10-fold compared with silver-free prostheses. Silver ion concentrations between 1.7 and 0.17 mg/L, corresponding roughly to 1/20 to 1/200 of the MIC of silver nitrate, stimulated biofilm formation by C. albicans.
Conclusions:
Serum proteins reduced the concentration of silver ions delivered from the surface of vascular prostheses to a subinhibitory level, which stimulated the attachment and biofilm formation of C. albicans on grafts. Silver collagen coating therefore seems to be unsuitable for the prevention of growth of C. albicans on vascular prostheses under physiological conditions.
Insights
Silver coatings on vascular prostheses can unexpectedly promote Candida albicans biofilm formation in the presence of serum. This suggests silver collagen coatings may be unsuitable for preventing yeast infections on grafts under physiological conditions.
Area of Science:
- Biomaterials science
- Medical microbiology
- Infectious diseases
Background:
- Silver possesses antimicrobial properties, commonly used to prevent microbial colonization on medical devices.
- Limited data exist on silver's impact on Candida biofilm formation on vascular prostheses.
Purpose of the Study:
- To investigate the effect of silver coating on vascular prostheses on Candida yeast biofilm formation in an in vitro model.
Main Methods:
- Vascular prosthesis material was co-cultivated with two Candida albicans strains.
- Microscopy, colony-forming units (cfu), and mitochondrial dehydrogenase activity were used to monitor biofilm attachment and growth.
Main Results:
- Silver collagen coatings significantly reduced Candida albicans biofilm in serum-free medium.
- In 50% serum, silver coatings paradoxically increased biofilm growth 2- to 10-fold.
- Sub-inhibitory silver ion concentrations (0.17–1.7 mg/L) stimulated Candida biofilm formation.
Conclusions:
- Serum proteins reduce delivered silver ion concentration to sub-inhibitory levels, promoting Candida albicans biofilm formation on grafts.
- Silver collagen coating appears unsuitable for preventing Candida albicans growth on vascular prostheses under physiological conditions.
