Related Experiment Videos
Effect of Pseudomonas aeruginosa concentration in experimental contact lens-related microbial keratitis
C A Lawin-Brüssel1, M F Refojo, F L Leong
1Eye Research Institute, Harvard Medical School, Boston, Massachusetts.
Abstract:
Pseudomonas aeruginosa adherence in vitro to perfilcon A (ionic, 71% H2O) extended wear soft contact lenses--both new and after 7 days of continuous wear on closed rabbit eyes--was found to be related directly to the bacterial concentration in the contaminating solution. Thirty rabbits wore perfilcon A lenses for 7 days with complete lid closure to mimic contact lens overwear. After 7 days, conjunctival cultures showed no growth of pathogens, but all corneas had developed epithelial cell exfoliation and/or epithelial defects and stromal edema. The lenses were then incubated in various concentrations (10(7), 10(6), 10(5), 10(4), and 10(2) colony-forming units per milliliter or saline control; n = 5/group) of P. aeruginosa suspensions and replaced on their respective corneas with tarsorrhaphies for an additional 48 h. By day 9, corneal thickness had increased significantly, and P. aeruginosa keratitis had developed in 13 of 25 bacterially exposed eyes but not in 5 control eyes. Although with decreasing P. aeruginosa concentration the prevalence of ulcerative microbial keratitis also decreased, the initial concentration of bacteria or the initial extent of soft contact lens-induced corneal damage had no influence on the ultimate clinical severity of the disease.
Insights
Bacterial concentration directly impacts Pseudomonas aeruginosa adherence to soft contact lenses. Overwear can cause corneal damage, increasing keratitis risk, though initial damage doesn't predict disease severity.
Area of Science:
- Ophthalmology
- Microbiology
- Biomaterials Science
Background:
- Extended wear of soft contact lenses, particularly ionic perfilcon A, is associated with ocular complications.
- Pseudomonas aeruginosa is a common pathogen implicated in microbial keratitis, a serious eye infection.
- Understanding bacterial adherence to contact lenses is crucial for preventing contact lens-related infections.
Purpose of the Study:
- To investigate the in vitro adherence of Pseudomonas aeruginosa to perfilcon A soft contact lenses.
- To evaluate the effect of continuous wear and bacterial concentration on Pseudomonas aeruginosa-induced keratitis in a rabbit model.
Main Methods:
- Perfilcon A soft contact lenses (new and after 7-day rabbit eye wear) were exposed to various concentrations of Pseudomonas aeruginosa.
- A rabbit model was used to assess the impact of contact lens overwear and subsequent bacterial challenge on corneal health.
- Corneal and conjunctival examinations, along with measurements of corneal thickness, were performed.
Main Results:
- Pseudomonas aeruginosa adherence in vitro was directly proportional to bacterial concentration.
- Seven days of soft contact lens wear in rabbits caused corneal epithelial defects and stromal edema, even without bacterial contamination.
- Subsequent bacterial challenge led to Pseudomonas aeruginosa keratitis in 52% of exposed eyes, with severity correlating to bacterial concentration but not initial corneal damage.
Conclusions:
- Bacterial concentration is a key factor in Pseudomonas aeruginosa adherence to soft contact lenses.
- Soft contact lens overwear compromises corneal integrity, predisposing eyes to infection.
- While bacterial load influences keratitis prevalence, pre-existing contact lens-induced corneal damage does not dictate disease severity.