Cultivation-independent analysis of worn spectacles using 16S rRNA sequencing

Backround: Surfaces with contact to the human body are usually contaminated with microorganisms and might be considered as fomites. The same applies for spectacles, but only little is known about their microbial load. Previous aerobic cultivation analyses from our group revealed a bacterial load strongly dominated by staphylococci. To better account for aerotolerant anaerobes, slow growing and yet-uncultivated bacteria, we performed a 16S rRNA gene sequencing approach.30 spectacles from university staff and students were swab-sampled at three sampling sites, each (nosepads, glasses and earclips). We sequenced the V1 – V3 region of bacterial 16S rRNA gene amplicons on an Illumina MiSeq platform using an optimized library preparation protocol. Results: 28 earclips, 29 nosepads and 28 glasses yielded good quality sequences, which were used for downstream analyses. After rarefication, 19 phyla and 665 genera of bacteria were detected. Actinobacteria (64%), Proteobacteria (22%), Firmicutes (7%) and Bacteroidetes (5%) were the dominant phyla. At genus level, just 13 genera accounted for 84% of the total sequences of all spectacles, with a prevalence of more than 1% abundance. Propionibacterium (57%), Corynebacterium (5%), Staphylococcus (4%), Pseudomonas, Sphingomonas and Lawsonella (3%, each), Paracoccus, Haemophilus, Burkholderia-Paraburkholderia and Capnocytophaga (2%, each) were the most abundant genera. Statistical analyses revealed a significantly higher bacterial diversity on the glasses compared to nosepads and earclips.Conclusion: Here, we report the first cultivation-independent composition of the bacteriota on worn spectacles and we provide an optimized protocol for 16S rRNA gene sequencing that can be used to identify a low biomass microbial community using swab sampling. We have shown that spectacles are significantly contaminated by bacteria, dominated by aerobic and anaerobic bacteria of mostly human skin and epithelia origin, and clearly including potentially pathogenic ones. They may play a role as fomites in especially clinical environments where transmission of pathogens could occur through spectacle contamination, and additionally contribute to eye and skin infections.