Used contact lenses harbor a diverse microbial community that includes commensal, environmental and pathogenic bacteria.  In a recent study, 75% of analyzed lotrafilcon A contact lenses that were worn for about 30 days contained organisms of the conjunctival, skin and ocular surface microbiome that had adhered. Organism diversity of the lens-adherent microbiome showed a significant increase in the lenses treated with polyhexamethylene biguanide-preserved multipurpose solution compared with peroxide solution.

The study assessed the microbiome adherence to contact lenses from 42 participants and identified 19 phyla and 167 genera of bacteria communities associated with use of lens care solutions. Proteobacteria was the most abundant phyla, followed by Firmicutes and Actinobacteria. The most abundant bacterial genera (>1% abundance) were Ralstonia, Enterococcus, Streptococcus, Halomonas, Corynebacterium, Staphylococcus, Acinetobacter, Shewanella, Rhodococcus and Cobetia.

The researchers suggest that the differences in diversity and abundance in the treated lens groups likely reflects the differences in antimicrobial activity of the two types of lens cleaning solutions. They also surmise that the difference in the design and material of lens storage cases and excipients from storage solutions as well as niche-specific competition between the microbes may also account for differences in biodiversity on stored lenses. Nevertheless, the researchers believe that future research must investigate the clinical relevance of these bacterial communities and the differences in bioburden they detected.