Anticoagulant Properties of Extracellular Slime Substance Produced by Staphylococcus Epidermidis

Biofilm and Foreign Body Infection the Significance to Capd-Associated Peritonitis

Microbial colonization of indwelling and implantable medical devices and prostheses is known to precede the formation of an adherent biofilm, such as is found on peritoneal catheters during CAPD. Micro-organismderived exopolysaccharides within the biofilm matrix seem to confer unique biological properties on this material, such as enhanced resistance to host defenses and antimicrobial agents. It has been proposed that an adherent biofilm is a major contributing factor in the development of foreign-body infections, including CAPD peritonitis. The source of organisms which lead to biofilm formation on peritoneal catheters is unknown but may include “seeding” at the time of surgical placement and migration from the subcutaneous tunnel via the inner cuff.

Strategies to inhibit biofilm development in industrial systems usually involve physical destruction of the biofilm and the use of biocides. Clinical success has been achieved by antimicrobial agents impregnated into or coated onto susceptible devices. Microbial adhesion to inanimate surfaces is a complex and multifaceted event. Continued research in this area, however, should increase our understanding of the factors involved underlying foreignbody infection.

The nature and role of microbial biofilm in infections associated with prosthetic devices

An understanding of the role of microbial biofilm in infections associated with prosthetic devices is essential for the implementation of successful treatment regimens.

Isolation and characterization of a highly specific serine endopeptidase from an oral strain of Staphylococcus epidermidis

Infection by Staphylococcus epidermidis, an opportunistic pathogen, has become a major problem due to the increased use of implanted medical devices and the growing number of patients who are therapeutically or infectiously immunosuppressed. These infections appear to proceed via modulation of the coagulation and complement systems. In this communication we describe the purification and characterization of a novel extracellular proteinase from an oral strain of S. epidermidis that can degrade fibrinogen, complement protein C5, and several other proteins. This proteinase has a strong preference for cleavage after glutamic acid residues, but not after aspartic acid. The S. epidermidis enzyme may be a multifunctional protein which not only provides this organism with both the ability to evade the complement defense system and to dysregulate the coagulation cascade, but also supplies nutrients for its growth through the degradation of Glu-rich proteins.

The slime of coagulase-negative staphylococci: biochemistry and relation to adherence

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.

Anticoagulant activity of a bacterial glycopeptide

The anticoagulant properties of myxalin, a glycopeptide secreted by a Gram negative bacterium strain (Myxococcus xanthus) are studied and compared to those of heparin. This soluble material exhibits an anticoagulant activity which implies the inhibition of some serine proteases, thrombin and factor Xa. In the presence of normal and antithrombin III-depleted plasma, myxalin inhibits the amidolytic activity of thrombin on synthetic chromogenic substrate as a function of its concentration, but fails to increase thrombin inactivation significantly in the presence of purified AT III. However, crossed immunoelectrophoresis data suggests that its antithrombi effect is mainly mediated by binding to the enzyme, rather than to AT III and probably differs from the catalytic activity of heparin which requires the presence of AT III. The anticoagulant process occurs without degradation of fibrinogen and can be neutralized by protamine.

Coagulase-negative staphylococci: incidence, pathogenicity, and treatment in the 1990s

Coagulase-negative staphylococci (CNS), which historically have been viewed as contaminants when recovered in culture media, are now recognized as opportunistic pathogens of increasing importance in hospital-acquired infections. They are frequently found colonizing prosthetic devices and intravenous lines. CNS are capable of producing a variety of infections including deep-seated infections such as endocarditis and meningitis. Staphylococcus epidermidis is the most commonly isolated CNS and it appears to be the most resistant to antibiotics, making antimicrobial therapy challenging. Treatment of the infection will very often require removal of a prosthetic device, if present. An adequate infection control program is imperative in prophylaxis against this infection.

Staphylococcal slime: a cautionary tale

Slime production by Staphylococcus epidermidis may be important in the adherence to and colonization of biomedical devices, and slime has been proposed to have various effects on the immune system. Attempts were made to isolate, purify, and chemically characterize slime from S. epidermidis cultivated under fluid on tryptic soy broth-agar medium. "Crude slime" from slime-producing strain RP-12 was characterized by a high galactose content. Similar materials in similar yields were isolated from slime-producing strain Kaplan, a non-slime-producing mutant, Kaplan-6A, and sterile medium controls, suggesting that crude slime was derived mainly from the medium. The occurrence of D- and L-galactose and pyruvate and sulfate residues and methylation analysis of these crude slime preparations, monitored by gas-liquid chromatography and mass spectrometry, showed that the agar was the main source of crude slime, suggesting that the preparation was largely an artifact of the growth and isolation procedures. Similar high-galactose-content preparations from both S. epidermidis and Staphylococcus aureus, assumed to be bacterial products and with a variety of biological activities, have been described by other investigators. Growth attached to a solid surface appears to be important for slime production. An accumulation of turned-over cell surface molecules and released macromolecules such as DNA may contribute to slime production. Avoidance of agar and development of a chemically defined medium for slime production are recommended for further studies.