Fungal-bacterial multispecies biofilms play a major role in failure of medical silicone devices, such as voice prostheses in laryngectomiy. In this study, we determined the effect of Lactobacilli supernatant (cell free) on mixed biofilm formation of fungi and bacteria on silicone in vitro. Lactobacilli supernatant inhibited the adhesion (90 min) of mixed fungi and bacteria species with an efficiency of >90%. Mixed biofilm formation and the metabolic activity of the biofilms were inhibited by 72.23% and 58.36% by Lactobacilli supernatant. The examination using confocal laser scanning microscopy and scanning electron microscopy confirmed that Lactobacilli supernatant inhibited the growth of mixed biofilm and damaged the cells. Moreover, Lactobacilli supernatant also inhibited Candida yeast-to-hyphal transition. Therefore, Lactobacilli supernatant may serve as a possible antibiofilm agent to limit biofilm formation on voice prostheses.
Mixed fungal-bacterial biofilm; Probiotic; Silicone voice prostheses
PMID: 29111321 DOI: 10.1016/j.micpath.2017.10.051
MORE EVIDENCE: SILICONE IS NOT INERT, BUT BIODEGRADABLE. DEGRADING TO FUNGI!
Degradation of Polymers in Nature
Environmental Information - Update
Polymers are a broad class of materials which are made from repeating units of smaller molecules called monomers. Polymers can be natural in origin, such as the lignin of tree branches, the starches of homemade bread, or the chitin of lobster shells. Other polymers are called synthetic, because they are made by humans from naturally-occurring materials. Examples include polyesters used in clothing, polystyrene used in home insulation, and silicones used in personal care and other products. Polymers are useful because of their strength and durability in many applications. However, after the useful life of a polymer is over, society desires that it degrade in the environment back to natural materials. This fact sheet first reviews the natural degradation of a wide variety of polymers, and then shows how the degradation of silicone polymers follows the same pattern.
Natural Degradation of Polymers
Degradation of all polymers follows a sequence in which the polymer is first converted to its monomers, after which the monomers are mineralized. Most polymers are too large to pass through cellular membranes, so they must first be depolymerized to small monomers before they can be absorbed and biodegraded within microbial cells. The initial breakdown of a polymer can result from a variety of physical, chemical, and biological forces , with chemical hydrolysis probably being the most important .
Health Environment & Regulatory Affairs (HERA)
Physical forces, such as heating/cooling, freezing/ thawing, or wetting/drying, can cause mechanical damage such as the cracking of polymeric materials . The growth of many fungi can also cause small-scale swelling and bursting, as the fungi penetrate the polymer solids . These physical forces deteriorate the polymer surfaces and create new surfaces for reacting with chemical and biochemical agents, a critical phenomenon in the degradation of solid polymers. For fluid polymers, the chemical and biological forces are more important.
Soil microbes can initiate the depolymerization of many natural polymers such as starch, cellulose, and hemicellulose [5, 6]. They secrete a variety of enzymes into the soil water, and these enzymes then begin the breakdown of the polymers. Other natural polymers such as lignin are quite resistant to breakdown, and nature has developed a system in which certain fungi secrete hydrogen peroxide and a specific enzyme, which act together to slowly initiate degradation [7, 8]. These reactions can also decompose synthetic polymers, such as polyacrylic acid and polyacrylamide [9, 10].
In addition, microbial exudates (other than enzymes) can create a micro-environment in which certain polymers become chemically unstable. For example, sulfur bacteria produce sulfuric acid from sulfide or sulfur . Many fungi secrete organic acids while decomposing plant materials [5, 11], while plant roots secrete both H+ and HCO - during the uptake of
3 nutrients . If these processes occur in the vicinity
of acid - or base - susceptible polymers, they may increase the degradation rates of the polymers.
Ref. n° 01-1112-01 1/4 © Copyright Dow Corning Corp., 1997. All rights reserved. Last Revision 07/98
Testing polymer degradation
The fact that polymers degrade in a sequence of abiotic and biological steps means that the standardized tests for measuring biodegradation of many small molecules do not realistically address what actually happens to a polymer in nature. For example, the OECD’s regulatory test, “Inherent Biodegradability in Soil,” tracks CO release over a
2 64 day period as a measure of biodegradation .
This test would only be relevant when the entire abiotic/biotic degradation sequence of a polymer occurs under the specific conditions of the test. In the case of silicones, this test would have completely missed the clay-catalyzed hydrolysis of the polymer and the identification of the monomer hydrolysis product. Subsequent reactions of the monomer, such as its biodegradation and volatilization/ atmospheric degradation, would probably have gone undetected, as well. In situations where a polymer’s monomeric units are not mineralized but are incorporated into growing cells, a simple C02 evolution test would again miss the point. The net effect of trying to force-fit the complex mechanisms of polymer degradation into a simple, standardized regulatory test means that misleading information about a polymer’s fate in the environment will be generated. For this reason, Dow Corning has published an extensive series of research studies designed to investigate the complete sequence of abiotic/biotic degradation of silicones in nature.
Ref. n° 01-1112-01 2/4 © Copyright Dow Corning Corp., 1997. All rights reserved. Last Revision 07/98
SO EVEN IN BUILDING MATERIALS SILICONE IS DEGRADING TO FUNGI AND DEVELOPING BIOFILMS?
OTHER TYPES OF SILICONE IMPLANTS ARE SHOWING EVIDENCE OF FUNGAL GROWTH?
ART PROJECTS MADE WITH SILICONE ARE DEGRADING TO FUNGI WITH EVIDENCE OF BIOFILMS?
MORE RESEARCH ON TYPES OF INMPLANTS DEVELOPING FUNGAL OVERGROWTH? Importance of fungus colonization in failure of silicone rubber percutaneous gastrostomy tubes (PEGs).
Iber FL1, Livak A, Patel M.
Silicone rubber PEG tubes or replacements were recov