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Microbial adherence on poly(methyl methacrylate) (PMMA) surfaces
1Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio 44106.
Abstract:
Infection remains a major complication following the use of implanted biomaterials. Often these infections are caused by low-virulence organisms or by a mixture of organisms (polymicrobial). In this study two methods were used to quantitate the bacteria which had adhered to poly(methyl methacrylate) (PMMA) samples. The bacteria were eluted from the sample using an ultrasonic cleaner. The number eluted was then counted by colony counts, which determines viable organisms and by particle counting which counts both viable and nonviable organisms. A known adherent strain of Staphylococcus epidermidis and a strain of Proteus mirabilis were used. In general the adherence of S. epidermidis was greater than that of Proteus. When the two organisms were used together, there was an alteration in the adherence pattern which generally increased the adherence of Proteus and had no effect or decreased the adherence of S. epidermidis. The use of both quantitation techniques provided important information on the adherence of organisms to PMMA to which gentamicin had been added. It was evident that organisms did adhere to the PMMA plus gentamicin samples but were not viable when eluted. The amount of adherence to PMMA plus gentamicin was similar to that of PMMA alone at 30 min but was markedly decreased at 24 h. There was a considerable dead biofilm mass on the PMMA plus gentamicin samples which might be a significant promoter of late infections by providing a surface attractive to other strains of bacteria.
Insights
Bacterial adherence to biomaterials like poly(methyl methacrylate) (PMMA) is a key factor in implant infections. This study quantifies bacterial adhesion to PMMA, finding that gentamicin-treated samples reduce viable bacteria but can still form dead biofilms.
Area of Science:
- Biomaterials Science
- Infectious Diseases
- Microbiology
Background:
- Implanted biomaterials are susceptible to infection, often by polymicrobial or low-virulence organisms.
- Understanding bacterial adherence to biomaterials is crucial for preventing implant-associated infections.
Purpose of the Study:
- To quantify bacterial adherence to poly(methyl methacrylate) (PMMA) using two distinct methods.
- To investigate the effect of gentamicin on bacterial adherence and viability on PMMA.
- To analyze the adherence patterns of Staphylococcus epidermidis and Proteus mirabilis, individually and in combination.
Main Methods:
- Bacteria were eluted from PMMA samples using ultrasonic cleaning.
- Quantification of adhered bacteria was performed using colony counts (viable organisms) and particle counting (viable and nonviable organisms).
- Experiments involved Staphylococcus epidermidis, Proteus mirabilis, and PMMA with and without gentamicin.
Main Results:
- Staphylococcus epidermidis generally showed higher adherence than Proteus mirabilis.
- Co-culture of bacteria altered adherence patterns, increasing Proteus mirabilis adherence and affecting Staphylococcus epidermidis adherence.
- PMMA with gentamicin showed adherence of nonviable organisms, with reduced adherence over time compared to PMMA alone.
- A significant dead biofilm mass was observed on PMMA with gentamicin.
Conclusions:
- Both viable and nonviable bacterial quantification methods provide valuable insights into adherence to PMMA.
- Gentamicin-treated PMMA reduces viable bacterial adherence but can lead to dead biofilm formation.
- Dead biofilms on gentamicin-treated PMMA may serve as a nidus for subsequent bacterial colonization and late infections.