Purpose: To investigate the effects of the long-term use of prostaglandin analogs for glaucoma treatment on the indigenous flora of the conjunctiva.
Methods: Bacterial isolates were collected from the conjunctival sacs of 68 patients at Miyata Eye Hospital from February to September 2014, who had been receiving continuous monotherapy with prostaglandin analogs for glaucoma for at least 1 year. Minimum inhibitory concentrations of levofloxacin, gatifloxacin, moxifloxacin, cefmenoxime, tobramycin, chloramphenicol, and erythromycin against the isolates were measured to determine susceptibility.
Results: The positive culture rate in all cases was 90.5% (57/63 eyes), and a total of 79 bacterial strains were isolated. The isolated bacteria included aerobic gram-positive cocci (8% Staphylococcus aureus and 41% Staphylococcus epidermidis), coagulase-negative staphylococci (5%), Streptococcus spp. (1%), Corynebacterium spp. (4%), gram-negative bacteria (4%), and the facultative anaerobe Propionibacterium acnes (33%). The positive culture rates for patients using 0.005% latanoprost (Xa group) and 0.004% travoprost (Tz group) were 88.9% and 92.6%, respectively, with no statistically significant difference in the composition of isolated bacteria between groups. Methicillin-resistant S. epidermidis (MRSE) was significantly more frequently isolated in the Xa group. The antimicrobial susceptibility rates of S. epidermidis were significantly lower in the Xa group for levofloxacin, gatifloxacin, moxifloxacin, and tobramycin.
Conclusions: The indigenous flora may be affected by the long-term use of prostaglandin analogs. The higher incidence of MRSE in the Xa group should be considered during the long-term, continuous administration of eye drops, such as in glaucoma treatment.