Evaluation of Aerobic Conjunctival Flora in Patients with Demodex Blepharitis

Objective: Demodex species are frequently found in blepharitis cases. This study aimed to compare the conjunctival flora of eyes with Demodex-positive blepharitis and Demodex-negative blepharitis with healthy individuals.

Methods: Eyelash epilation was performed to detect Demodex from 44 eyes of 44 patients with chronic blepharitis and 44 eyes of 44 healthy controls and examined under a microscope. A conjunctival swab was taken from the same eye and inoculated on eosin methylene blue agar, Sabouraud dextrose agar, chocolate agar, and 5% sheep blood agar. Aerobic conjunctival flora was evaluated among Demodex-positive blepharitis, Demodex-negative blepharitis and healthy eyes.

Results: Demodex spp. was detected in 3 (6.8%) of 44 healthy controls and 24 (54.5%) of 44 patients with blepharitis. The most frequently isolated bacteria in healthy controls were coagulase-negative Staphylococci (CNS) spp. (n=32, 72.7%), Streptococcus spp. (n=16, 36.4%), Corynebacterium spp. (n=13, 29.5%). The most frequently isolated bacteria in Demodex-positive blepharitis were CNS spp. (n=14, 58.3%), Staphylococcus aureus (n=11, 45.8%), Corynebacterium spp. (n=7, 29.2%). In Demodex-negative blepharitis, CNS (n=10, 50.0%), S. aureus (n=10, 50.0%), Corynebacterium spp. (n=5, 25.0%) were most commonly isolated. S. aureus growth was significantly increased in the Demodex negative and positive blepharitis groups compared with the healthy group (p=0.001 and p=0.002, respectively). Although CNS spp. growth decreased in both groups with Demodex-negative and positive blepharitis compared with the healthy group; the decrease was significant only in those with Demodex-negative blepharitis (p=0.045). In terms of other bacterial growth, there was no significant difference between healthy eyes and Demodex positive and negative eyes with blepharitis.

Conclusion: We found that Demodex blepharitis has no significant effect on conjunctival flora. Blepharitis itself may be the main factor in changes in the conjunctival flora.