Factors influencing bacterial adhesion to contact lenses.
ABSTRACT The process of any contact lens related keratitis generally starts with the adhesion of opportunistic pathogens to contact lens surface. This article focuses on identifying the factors which have been reported to affect bacterial adhesion to contact lenses. Adhesion to lenses differs between various genera/species/strains of bacteria. Pseudomonas aeruginosa, which is the predominant causative organism, adheres in the highest numbers to both hydrogel and silicone hydrogel lenses in vitro. The adhesion of this strain reaches maximum numbers within 1h in most in vitro studies and a biofilm has generally formed within 24 h of cells adhering to the lens surface. Physical and chemical properties of contact lens material affect bacterial adhesion. The water content of hydroxyethylmethacrylate (HEMA)-based lenses and their iconicity affect the ability of bacteria to adhere. The higher hydrophobicity of silicone hydrogel lenses compared to HEMA-based lenses has been implicated in the higher numbers of bacteria that can adhere to their surfaces. Lens wear has different effects on bacterial adhesion, partly due to differences between wearers, responses of bacterial strains and the ability of certain tear film proteins when bound to a lens surface to kill certain types of bacteria.
Article: Bacterial adhesion to conventional hydrogel and new silicone-hydrogel contact lens materials.[show abstract] [hide abstract]
ABSTRACT: As bacterial adhesion to contact lenses may contribute to the pathogenesis of keratitis, the aim of our study was to investigate in vitro adhesion of clinically relevant bacteria to conventional hydrogel (standard HEMA) and silicone-hydrogel contact lenses using a bioluminescent ATP assay. Four types of unworn contact lenses (Etafilcon A, Galyfilcon A, Balafilcon A, Lotrafilcon B) were incubated with Staphylococcus epidermidis (two different strains) and Pseudomonas aeruginosa suspended in phosphate buffered saline (PBS). Lenses were placed with the posterior surface facing up and were incubated in the bacterial suspension for 4 hours at 37 degrees C. Bacterial binding was then measured and studied by bioluminescent ATP assay. Six replicate experiments were performed for each lens and strain. Adhesion of all species of bacteria to standard HEMA contact lenses (Etafilcon A) was found to be significantly lower than that of three types of silicone-hydrogel contact lenses, whereas Lotrafilcon B material showed the highest level of bacterial binding. Differences between species in the overall level of adhesion to the different types of contact lenses were observed. Adhesion of P. aeruginosa was typically at least 20 times greater than that observed with both S. epidermidis strains. Conventional hydrogel contact lenses exhibit significantly lower bacterial adhesion in vitro than silicone-hydrogel ones. This could be due to the greater hydrophobicity but also to the higher oxygen transmissibility of silicone-hydrogel lenses.Albrecht von Graæes Archiv für Ophthalmologie 03/2008; 246(2):267-73. · 2.17 Impact Factor
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ABSTRACT: The aim of this study was to investigate a method to reduce the frequency of uterine reoperation with no persistent lesion and to identify factors predictive of persistent or recurrent lesions. Of 505 conizations performed by the same surgeon, 71 had positive margins (average patient age = 35.7 +/- 7.7 years). The patients underwent either immediate reoperation or monitoring with a Pap smear and colposcopy. Histologic assessment of the cervical cone after conization showed positive margins in 14.1% of cases [endocervical and exocervical margins affected in 50 of 505 (9.9%) and 21 of 505 (4.2%) cases, respectively]. Of 59 of these patients (83.1%) who underwent follow-up monitoring over an average of 35.2 months (range: 2.6-180. 8), 12 patients (average age: 40.8 +/- 6.4 years) underwent immediate hysterectomy and 47 (average age 34.0 +/- 7.4 years) benefited from monitoring first [secondary discovery of 19 persistent lesions within 6 months and 9 recurrences within 18 months on average (range: 8.8-48 months)]. Of the 9 patients with recurrent lesions, 7 underwent reintervention and 2 monitoring. Of the 19 patients with persistent lesions, 18 underwent reintervention and 1 monitoring. Normal histology was observed in 29.4% of patients undergoing secondary reoperation for an abnormal smear compared with 66.7% of patients undergoing immediate reoperation (P = 0.04). Severity of lesion and age of patients could not be used to predict the incidence of a persistent or recurring lesion. Seventy-nine percent of conizations had positive endocervical margins in patients with a recurring or persistent lesion compared with 48% in patients with normal follow-up (P = 0.03). Cytology and colposcopy follow-up in cases of positive conization margins may help to establish justification for the choice of reoperation, thereby limiting morbidity following repeated surgery.Gynecologic Oncology 04/2000; 76(3):311-4. · 3.89 Impact Factor
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ABSTRACT: Staphylococcus epidermidis is a major causative agent of infectious keratitis associated with contact lens wear. Adhesion of this bacterium to contact lenses may contribute to the pathogenesis of infection and could be influenced by lens surface properties, packaging/storage solutions, and vary among different strains according to the level or type of adhesins expressed. Adhesion of six clinical isolates of S. epidermidis to three different contact lens materials was tested. Adhesion assays were performed on lenses immediately after removal from their packages, and also after lenses were soaked in sterile phosphate buffered saline (PBS) for 7 days to dilute the packaging solution. For lenses tested immediately upon removal from their packaging, adhesion to polymacon (in PBS with 0.1% polyvinyl alcohol) was significantly greater than to etafilcon A (in borate buffered saline) and vifilcon A (in PBS). After soaking, adhesion to polymacon lenses was significantly less than to the other lens materials. This pattern was consistent for all strains, although major differences in baseline adhesion levels existed between strains, with exopolysaccharide (slime)-positive bacteria being more adherent to lenses. Properties of contact lens materials were not the sole determinant of viable S. epidermidis adhesion to lenses. Strain variability, including levels of exopolysaccharide expression, and the solution used for lens immersion also influenced adhesion.Optometry and Vision Science 10/1996; 73(9):590-4. · 2.11 Impact Factor