Ocular flora in patients undergoing intravitreal injections: antibiotic resistance patterns and susceptibility to antiseptic picloxydine.

Aim: To study antibiotic resistance patterns and susceptibility to eye antiseptic picloxydine of conjunctival flora in patients undergoing intravitreal injections (IVIs).
Methods: Conjunctival swabs were taken in 4 groups of patients, 20 patients in each group ( n =80): without IVIs and ophthalmic operations in history (group N1; control group); with the first IVI and antibiotic eye drops Tobrex applied 3d before IVI and 5d after it (group N2); with 20 or more IVIs and repeated courses of antibiotic eye drops (group N3); with the first IVI and antiseptic eye drops Vitabact (picloxydine) applied 3d before IVI and 5d after it (group N4). In groups N2 and N4 swabs were taken at baseline and after the treatment. Efficacy of picloxydine in inhibition of growth of conjunctival isolates susceptible and resistant to antibiotic was studied in vitro . Minimal inhibition concentrations (MIC) were determined with microdilution test.
Results: Two of the three patients who had to undergo the IVI procedure showed conjunctiva bacterial contamination. Along with few Staphylococcus aureus and Gram-negative isolates susceptible to most antibiotics, the majority (71%-77%) of causative agents were coagulase-negative Staphylococci (CoNS), 40%-50% of which were multidrug resistant (MDR). Eye disinfection in the operating room and peri-injection courses of Tobrex or Vitabact resulted in total elimination of isolates found at baseline. However, in 10% and 20% of patients, respectively, recolonization of the conjunctiva with differing strains occurred. In patients with repeated IVI and Tobrex/Maxitrol treatment, the conjunctival flora showed high resistance rates: 90% of CoNS were MDR. In the in vitro study, picloxydine showed bactericidal effect against Staphylococci isolates both antibiotic resistant and susceptible with MIC≥13.56 µg/mL. Incubation of bacteria for 15min in Vitabact eye drops, commercially available form of picloxydine, 434 µg/mL, showed total loss of colony forming units of all tested isolates including Pseudomonas aeruginosa .
Conclusion: The confirmed efficacy of eye antiseptic picloxydine against conjunctival bacterial isolates and the presence of its commercial form, 0.05% eye drops, convenient for use by patients before and after injection, make this eye antiseptic promising for prophylaxis of IVI-associated infectious complications.
(International Journal of Ophthalmology Press.)