Effects of minocycline on the ocular flora of patients with acne rosacea or seborrheic blepharitis

Purpose. To assess the effect of minocycline on the ocular flora in patients with acne rosacea or blepharitis. Methods. A total of ten patients were enrolled in this prospective study, with six patients diagnosed with acne rosacea with concomitant meibomianitis, two patients with acne rosacea without concomitant ocular involvement, and two patients with seborrheic blepharitis. The eyelids and conjunctiva of both eyes were cultured before the initiation of systemic minocycline therapy, after 3 months of active therapy, and 3 months after the discontinuation of therapy. Isolated bacteria were identified and quantified, and antibiotic susceptibility was determined. Results. The colony-forming units (CFU) isolated from the eyelids significantly decreased after a 3-month treatment with minocycline (P = 0.0013). The CFU significantly increased to approach that of the baseline with the discontinuation of minocycline (P = 0.0275). The most common isolated bacteria, including coagulase-negative Staphylococcus (CNS), Staphylococcus aureus (S. aureus), and Propionibacterium acne (P. acne), except for corynebacterium, had a significant decrease in bacterial count with minocycline therapy compared with baseline (P < 0.05). There was a trend in the decrease of bacterial CFU isolated from the conjunctiva with minocycline therapy, although this was not statistically significant (P = 0.1955). Four of the ten patients carried tetracycline-resistant CNS strains, but none of the S. aureus or P. acne isolated at baseline was resistant to tetracycline. All six patients with acne rosacea and concomitant meibomianitis had marked clinical improvement. Conclusion. Minocycline effectively decreased eyelid bacterial flora in patients with acne rosacea or blepharitis. One of the mechanisms of newer generation tetracycline analogues may be a decrease or elimination of bacterial flora from the eyelids.