Evaluation of Aerobic Conjunctival Flora in Patients with Demodex Blepharitis

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.

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.

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.

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.