Purpose: The aims of our study were to compare the ocular microbial communities of humans with and without blepharitis in an attempt to elucidate which microorganisms may cause blepharitis.

Methods: Bacterial 16S rRNA genes of eyelash and tear samples from seven blepharitis patients and four healthy controls were sequenced using a pyrosequencing method, and their bacterial community structures were compared bioinformatically.

Results: Phylotypic analysis demonstrated that eyelash and tear samples had highly diverse bacterial communities with many previously undescribed bacteria. Bacterial communities in eyelash samples from subjects with blepharitis were less diverse than those from healthy controls, while the bacterial communities of tear subjects with blepharitis were more diverse than those of healthy subjects. Statistical analyses using UniFrac and a principle coordinate analysis showed that the bacterial communities of tear samples from subjects with blepharitis were well clustered, regardless of individual, while the bacterial communities of all eyelash samples and healthy tear samples were not well clustered due to high interpersonal variability. Bioinformatic analysis revealed that Propionibacterium, Staphylococcus, Streptophyta, Corynebacterium, and Enhydrobacter were the common ocular bacteria. An increase of Staphylococcus, Streptophyta, Corynebacterium, and Enhydrobacter, and a decrease of Propionibacterium were observed from blepharitis subjects, in terms of the relative abundances.

Conclusions: Higher abundances of Streptophyta, Corynebacterium, and Enhydrobacter in blepharitis subjects suggested that human blepharitis might be induced by the infestations of pollens, dusts, and soil particles. These results will provide valuable information for the prevention and treatment of human blepharitis based on ocular microbial flora.