Gram negative bacillus: the most frequent contaminant in worn soft contact lenses

Abstract

Bacteria are the most frequent contaminants in contact lenses. <em><strong>Objective:</strong></em> The aim of this study is to identify the type of microbiological deposits in worn soft contact lenses. Materials and <em><strong>Methods:</strong></em> 100 soft contact lenses from wearers or used in the optical shops were collected, 25 for each group of the Food and Drugs Administrations, (FDA) (group 1, 2, 3, and 4 according to water content and polymer ionicity). Contact lenses were stored for 20 days in their respective individual cases. Each lens was directly observed in a slit lamp to classify visible deposits according to RUDKO criterion, blue lactophenol direct examination and microbiological cultures. <em><strong>Results:</strong></em> According to the Food and Drugs Administrations groups, the microbial contamination in group 1 was 80% (20/25) with bacteria and 8% (2/25) with fungi. In group 2 was 88% (22/25) with bacteria, and 4% (1/25) with fungi. In group 3 was 72% (18/25) with bacteria, and 20% (5/25) with fungi. In group 4 was 80% (20/25) with bacteria, and 12% (3/25) with fungi. Fungi presence was always concomitant with bacteria. According to Rudko criterion 43.2% of category I lenses (17/37) had microbiological contamination with bacteria or fungi. 100% of category II lenses (56/56) and category IV lenses (7/7) were contaminated. The most frequent type of bacteria identified in the culture was bacillus and gram-negative coccobacillus. Conclusions: gram-negative bacilli were the microorganisms most found in worn soft contact lenses after 20 days of storage.