An Essential Role for Coagulase inStaphylococcus aureusBiofilm Development Reveals New Therapeutic Possibilities for Device-Related Infections

Abstract

High-level resistance to antimicrobial drugs is a major factor in the pathogenesis of chronic Staphylococcus aureus biofilm-associated, medical device-related infections. Antimicrobial susceptibility analysis revealed that biofilms grown for ≤ 24 hours on biomaterials conditioned with human plasma under venous shear in iron-free cell culture medium were significantly more susceptible to antistaphylococcal antibiotics. Biofilms formed under these physiologically relevant conditions were regulated by SaeRS and dependent on coagulase-catalyzed conversion of fibrinogen into fibrin. In contrast, SarA-regulated biofilms formed on uncoated polystyrene in nutrient-rich bacteriological medium were mediated by the previously characterized biofilm factors poly-N-acetyl glucosamine, fibronectin-binding proteins, or autolytic activity and were antibiotic resistant. Coagulase-mediated biofilms exhibited increased antimicrobial resistance over time (>48 hours) but were always susceptible to dispersal by the fibrinolytic enzymes plasmin or nattokinase. Biofilms recovered from infected central venous catheters in a rat model of device-related infection were dispersed by nattokinase, supporting the important role of the biofilm phenotype and identifying a potentially new therapeutic approach with antimicrobials and fibrinolytic drugs, particularly during the early stages of device-related infection.

In Vitro Approach for Identification of the Most Effective Agents for Antimicrobial Lock Therapy in the Treatment of Intravascular Catheter-Related Infections Caused by Staphylococcus aureus

“…We previously reported that vancomycin and rifampin concentrations as low as 1 mg/ml inactivated biofilms formed in this assay; however, vancomycin was less effective versus three-and five-day-old biofilm, and rifampin required increasing concentrations of 4 to 8 mg/ml to inactivate mature biofilm (14). Tigecycline concentrations of Ն128 g/ml inactivated biofilm formed over 24 h, while 4 mg/ml proved effective against more mature biofilms formed over 3 and 5 days (Fig.…”

“…However, when the environmental growth conditions in the host are considered, such as nutrient availability in vivo and the rapid conditioning of implanted device surfaces by the extracellular proteins fibronectin, fibrinogen, and collagen, the relevance of biofilm mechanisms already elucidated under in vitro conditions must come into question, as they may not be as important as once thought. To address this concern, we employed our recently described in vitro biofilm assay, which more closely mimics the physiological environment that is proposed to exist during the pathogenesis of an S. aureus catheter-related infection involving biofilm mediated by the enzyme coagulase (14). Using this more appropriate assay facilitated a more clinically relevant investigation that examined the effects of a range of commonly used antibiotics and antiseptic agents against a number of reference and clinical staphylococcal isolates (14).…”

“…Microtiter plate biofilm assays were carried out as described previously (14). Briefly, blood (approximately 40 ml) was drawn from a healthy volunteer using the S-Monovette system (Sarstedt) containing heparin or EDTA (15).…”

Impact of sarA and Phenol-Soluble Modulins on the Pathogenesis of Osteomyelitis in Diverse Clinical Isolates of Staphylococcus aureus

“…However, this conclusion must be interpreted with caution. For instance, under in vitro conditions, the relative impact of sarA versus that of the saePQRS (saeRS) regulatory locus on biofilm formation was recently shown to be dependent on the medium used to carry out the biofilm assay (22). Moreover, mutation of saeRS in the USA300 strain LAC was shown to limit virulence in a murine model of posttraumatic osteomyelitis owing to the increased production of the extracellular protease aureolysin, which results in the decreased accumulation of phenol-soluble modulins (PSMs) that would otherwise promote cytotoxicity for osteoblasts and bone destruction (23).…”

Tissue Plasminogen Activator Coating on Implant Surfaces Reduces Staphylococcus aureus Biofilm Formation

“…All of the above-mentioned infections occur inside the human body; therefore, host factors play an essential role in their development. Local coagulation induced by S. aureus coagulases promotes bacterial attachment to the surfaces of implants (8)(9)(10). After an initial adhesion phase, bacteria divide, deposit an extracellular matrix, and develop complex threedimensional biofilm structures.…”