Delineation of the bacterial composition in exogenous endophthalmitis using 16S rDNA sequencing

To determine the bacterial spectrum of exogenous endophthalmitis of different origins, namely, posttraumatic, postcataract surgery, filtering bleb-associated, and intravitreal treatment-related endophthalmitis, using the 16S rDNA sequencing method.

Aqueous humor or vitreous humor samples were collected from 24 endophthalmitis patients. Traditional cultivation and 16S rDNA sequencing were conducted with these samples. Three senile cataract controls and one intraocular irrigating solution were used as sequencing control.

Eleven of the 24 samples (45.8%) obtained positive bacterial cultivation, and each sample positive for only one species. The 11 culture-positive species could all be identified in their corresponding sequencing results, but only four strains being the top one pathogen in the sequencing. A total of 567 species were isolated using 16S rDNA sequencing, with the top five species being Pseudomonas sp., Staphylococcus epidermidis, Staphylococcus sp., Streptococcus sp., and Enterococcus faecalis. The dominant bacterial strains varied among the different endophthalmitis categories but with no significant difference in the overall bacterial spectrum. Bacterial atlas containing Pseudomonas, Streptococcus, Staphylococcus, Actinomycetales_unclassified, Thermus, and Janibacter was shared by the four categories. Aqueous humor bacterial profile showed a higher overlap with contaminating bacteria from the environment.

16S rDNA sequencing is more efficient for endophthalmitis pathogen screening than the traditional cultivation method in terms of positive detection rate and the number of bacteria identified. But the risk of environmental contamination exists when using 16S rDNA sequencing method for endophthalmitis diagnosis. Different categories of endophthalmitis displayed diversified bacterial composition.