Bacterial interactions with contact lenses; effects of lens material, lenswear and microbial physiology

Contact lens wear is a successful form of vision correction. However, adver se responses can occur during wear. Many of these adverse responses are pro duced as a consequence of bacterial colonization of the lens. The present s tudy demonstrated that during asymptomatic contact lens wear lenses are col onized by low levels of bacteria with gram-positive bacteria, such as coagu lase negative staphylococci, predominating. Gram-negative bacteria are freq uently the causative agents of adverse responses during contact lens wear. Measuring the adhesion of different strains and/or species of bacteria to d ifferent contact lens materials demonstrated considerable differences. In p articular, Pseudomonas aeruginosa strains Paer1 and 6294 and Aeromonas hydr ophilia strain Ahyd003 adhered in larger numbers to the highly oxygen perme able contact lenses Balafilcon A compared to hydrogel lenses manufactured f rom either Etafilcon A or HEMA. Furthermore, after Balafilcon A lenses had been worn for 6 h during the day bacteria were able to adhere in greater nu mbers to the worn lenses compared to the unworn lenses with increases in ad hesion ranging from 243% to 1393%. However, wearing Etafilcon A lenses usua lly resulted in a decrease in adhesion (22-48%). Bacteria were able to grow after adhesion to lenses soaked in artificial tear fluid and formed biofil ms, visualized by scanning confocal microscopy. Chemostat grown bacterial c ultures were utilized to enable control of bacterial growth conditions and bacteria were shown to adhere in the greatest numbers if grown under low te mperature (25 degreesC compared to 37 degreesC). The changes in growth temp erature was shown, using 2D gel electrophoresis, to change the expression o f cell-surface proteins and, using ID gel electrophoresis, to change the ex pression of surface lipopolysaccharide of P. aeruginosa Paer1. Thus, these surface changes would have been likely to have mediated the increased adhes ion to Etafilcon A contact lenses. (C) 2001 Elsevier Science Ltd. All right s reserved.