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The slime of coagulase-negative staphylococci: biochemistry and relation to adherence
M Hussain1, M H Wilcox, P J White
1Department of Molecular Biology and Biotechnology, The University, Sheffield, UK.
Abstract:
In recent years, infections of implanted plastic devices by coagulase-negative staphylococci have become a major cause of septicaemia in human patients. The causal bacterial species is usually Staphylococcus epidermidis and these organisms grow as a biofilm adherent to a solid surface. Several methods have been introduced to assess the mass of adherent bacteria and the slimy matrix in which they are embedded. Some methods measure total biofilm, others measure the organisms or the slime alone. In vitro, the type of medium, the atmosphere during incubation, and the nature of the solid surface, affect the quantity of biofilm that is formed. In most studies on the chemistry of the slime, the material used was formed on complex media solidified with agar. Contamination by ingredients of the media or by agar may not always have been recognised. Recent work with chemically defined medium (liquid or solidified with silica gel) shows that the slime is a mixture of about 80% (w/w) teichoic acid and 20% protein. Growth as a biofilm may protect the staphylococci from antibiotics. At present, the greatest success in preventing infection has come from improved surgical techniques during the insertion of implants.
Insights
Coagulase-negative staphylococci form biofilms on plastic implants, causing infections. Biofilm slime is primarily teichoic acid and protein, potentially protecting bacteria from antibiotics.
Area of Science:
- Microbiology
- Biomaterials Science
- Infectious Diseases
Background:
- Coagulase-negative staphylococci, particularly Staphylococcus epidermidis, frequently infect implanted plastic devices.
- Bacterial biofilms on implants are a significant cause of human septicaemia.
- Existing methods for biofilm assessment vary in what they measure (total biofilm, bacteria, or matrix).
Purpose of the Study:
- To investigate the composition of staphylococcal biofilms formed on plastic implants.
- To understand factors influencing biofilm formation in vitro.
- To clarify the chemical nature of the biofilm matrix.
Main Methods:
- Culturing Staphylococcus epidermidis in vitro under varying conditions (medium, atmosphere, surface).
- Utilizing chemically defined media (liquid or silica gel solidified) to avoid contamination.
- Analyzing the composition of the formed biofilm matrix.
Main Results:
- Biofilm formation is influenced by the culture medium, incubation atmosphere, and surface type.
- Using chemically defined media revealed the biofilm matrix is approximately 80% teichoic acid and 20% protein.
- Biofilm growth may confer antibiotic resistance to staphylococci.
Conclusions:
- The biofilm matrix produced by Staphylococcus epidermidis on plastic implants has a defined chemical composition.
- Understanding biofilm composition is crucial for developing strategies against implant-associated infections.
- Improved surgical techniques remain the most effective preventive measure currently.