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An assay of Staphylococcus epidermidis biofilm responses to therapeutic agents
1South Saskatchewan Hospital Center, Regina, Canada.
Abstract:
Implant-associated infections tend to become persistent, resisting host defences and antibiotic therapy. Routine clinical laboratory testing of bacterial isolates in the fluid phase for antibiotic susceptibility may not be predictive of therapeutic outcomes and therefore a number of antibiotic regimes have been formulated empirically. The resistance of implant-associated infections has been ascribed to the production by bacteria, when adherent to the implant surface, of a shielding matrix of polymerized carbohydrates protecting the enclosed bacteria from immune defences and antibiotics. This complex of surface, bacteria and matrix is termed a biofilm. We describe a technique to evaluate the efficacy of antimicrobial agents directed against biofilm-forming strains of Staphylococcus epidermidis (a major cause of implant infections) utilizing standardized biofilm preparations formed on glass. The impact of the antimicrobial agents was assessed quantally using the end-point of permanent cessation of metabolic activity (cell death) of the entire biofilm determined by the loss of ability to reduce 2,3,5-triphenyltetrazolium chloride to a visible red intracellular precipitate of formazan. The relative rate of action of differing antimicrobial agents could be determined by the minimum period of exposure of the biofilm to the agents that is required to bring about sterilization, the clinically relevant marker. A wide range of antimicrobial substances could be evaluated, including chemical disinfectants, immunoreactive substances, antibiotics; singly and in combination; and the modifying effects of interaction with non-antibacterial therapeutic agents and other environmental factors. The technique is simple, inexpensive, reproducible and readily adaptable to the clinical situation where evaluation of therapeutic regimes for individual cases of prosthetic device-associated infection is required routinely with despatch and ease of interpretation.
Insights
This study presents a new method to test antimicrobial efficacy against Staphylococcus epidermidis biofilms, crucial for implant infections. The technique accurately assesses treatment effectiveness, aiding in better clinical decisions for prosthetic device infections.
Area of Science:
- Microbiology
- Biotechnology
- Infectious Diseases
Background:
- Implant-associated infections are persistent due to bacterial biofilms resisting treatment.
- Standard laboratory tests for antibiotic susceptibility may not predict clinical outcomes.
- Biofilms shield bacteria on implant surfaces from host defenses and antibiotics.
Purpose of the Study:
- To describe a novel technique for evaluating antimicrobial agents against Staphylococcus epidermidis biofilms.
- To assess the efficacy of various antimicrobial substances and combinations.
- To provide a reproducible method for clinical application in prosthetic device infections.
Main Methods:
- Standardized biofilms of Staphylococcus epidermidis were formed on glass surfaces.
- Antimicrobial agent impact was measured by permanent cessation of metabolic activity (cell death).
- Quantal assessment used the reduction of 2,3,5-triphenyltetrazolium chloride as an indicator.
Main Results:
- The technique determines the minimum exposure time required for biofilm sterilization.
- A broad range of antimicrobial substances, including disinfectants and antibiotics, were evaluated.
- The method assessed combinations and interactions with other therapeutic agents and environmental factors.
Conclusions:
- The developed technique is simple, inexpensive, and reproducible for evaluating antimicrobial efficacy against biofilms.
- It is readily adaptable for routine clinical use to guide treatment strategies for implant-associated infections.
- This method offers a clinically relevant marker for assessing therapeutic regimes with ease of interpretation.