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Effects of vancomycin, daptomycin, fosfomycin, tigecycline, and ceftriaxone on Staphylococcus epidermidis biofilms
Stefan Hajdu1, Andrea Lassnigg, Wolfgang Graninger
1Department of Trauma Surgery, Medical University of Vienna, Vienna, Austria.
Abstract:
Infection of medical implanted material is associated with considerable morbidity and costs. In the following work, we investigated the effects of vancomycin, daptomycin, fosfomycin, tigecycline, and ceftriaxone on biofilms formed by Staphylococcus epidermidis isolates causative for implant infection and catheter-associated bacteremia. Biofilms were studied using the static microtiter plate model and incubated with the antibiotics increasing the concentration from 1x to 128 x the minimal inhibitory concentration (MIC) of the respective isolate tested. To quantify the reduction of the biomass, the optical density ratio (ODr) of stained biofilms and the number of growing bacteria were determined. Incubation of the staphylococcal biofilms with the antibiotics decreased the biofilm ODr (at baseline = 1) for ceftriaxone (0.83 +/- 0.48) but minimally only for fosfomycin (0.96 +/- 0.64), daptomycin (1.05 +/- 0.59), tigecycline (1.18 +/- 0.66), and vancomycin (0.98 +/- 0.44) at exceedingly high concentrations of 128 x MIC. The significant reduction of the bacterial growth was not achieved for all antibiotics, not even at the highest concentrations tested. Using higher doses of the antibiotics may be of some value in the treatment of biofilm-associated infections, although effects are seen only at clinically unachievable doses. However, to eradicate the staphylococcal biofilm, additional measures like debridement and/or removal of the implant are needed.
Insights
This study examined antibiotics against Staphylococcus epidermidis biofilms. High antibiotic concentrations showed minimal impact on biofilm reduction, indicating additional measures are crucial for treating implant infections.
Area of Science:
- Microbiology
- Infectious Diseases
- Biomedical Engineering
Background:
- Medical implant infections are a significant cause of morbidity and healthcare costs.
- Staphylococcus epidermidis is a common pathogen in implant-associated infections and catheter-associated bacteremia.
- Bacterial biofilms on implanted materials are notoriously difficult to eradicate.
Purpose of the Study:
- To investigate the efficacy of vancomycin, daptomycin, fosfomycin, tigecycline, and ceftriaxone against Staphylococcus epidermidis biofilms.
- To quantify the reduction in biofilm biomass and bacterial growth when exposed to various antibiotic concentrations.
- To assess the potential of these antibiotics in treating biofilm-associated infections.
Main Methods:
- Utilized a static microtiter plate model to cultivate Staphylococcus epidermidis biofilms.
- Exposed biofilms to a range of antibiotic concentrations, from 1x to 128x the minimal inhibitory concentration (MIC).
- Quantified biofilm biomass using optical density ratio (ODr) and determined the number of viable bacteria.
Main Results:
- Ceftriaxone showed a slight decrease in biofilm ODr (0.83 +/- 0.48).
- Fosfomycin, daptomycin, tigecycline, and vancomycin demonstrated minimal reduction in biofilm biomass at 128x MIC.
- Significant reduction in bacterial growth was not consistently achieved across all tested antibiotics, even at high concentrations.
Conclusions:
- Antibiotics tested showed limited efficacy in reducing Staphylococcus epidermidis biofilms, even at clinically unachievable high doses.
- Higher antibiotic doses may offer some benefit but are unlikely to eradicate biofilms alone.
- Effective treatment of staphylococcal biofilm infections necessitates adjunctive strategies such as debridement or implant removal.
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