Changes in antibiotic resistance patterns of conjunctival flora due to repeated use of topical antibiotics after intravitreal injection

Ophthalmology. 2012 Jul;119(7):1420-4. doi: 10.1016/j.ophtha.2012.01.016. Epub 2012 Mar 13.


Objective: To determine the effect of repeated intermittent use of topical antibiotics after intravitreal injections on conjunctival bacterial flora and antibiotic resistance.

Design: Cross-sectional case-control study.

Participants and controls: A total of 80 eyes of 40 patients were enrolled (40 study eyes, 40 control eyes). Patients were enrolled with unilateral exudative age-related macular degeneration who had received at least 3 prior intravitreal injections with use of postinjection topical antibiotics. Patients had received an average of 7 (range, 3-13) intravitreal injections before enrollment.

Methods: At the time of enrollment, the inferior fornix of the treated eye was swept with a culture swab before use of povidone iodine; the inferior fornix of the fellow eye was also cultured and served as a control. The culture and sensitivity data from the study and control eyes were analyzed.

Main outcome measures: The rate of antibiotic resistance among the conjunctival bacterial flora of the study eyes and control eyes.

Results: A total of 80 eyes of 40 patients were enrolled in the study; 29 patients used trimethoprim/polymyxin B drops, and 11 patients used fluoroquinolone drops after each injection. A total of 58 bacterial colonies were isolated from 50 eyes. There were no significant differences in bacterial species or culture positivity rates between study and control eyes. Coagulase-negative staphylococcus accounted for 41 of the 58 bacterial colonies (71%). There was a 63.6% resistance rate to fluoroquinolones among study eyes compared with 32.1% among control eyes (P < 0.05). In the subset of 11 study eyes using fluoroquinolone drops for 4 days after injection, there was an 87.5% resistance rate compared with 25.0% in matched control eyes (P = 0.04). There was no significant difference in trimethoprim resistance rates between study and control eyes: Four of 14 study eyes (28.6%) showed resistance compared with 5 of 18 control eyes (27.7%) (P = 1.0).

Conclusions: Use of fluoroquinolone drops after intravitreal injection leads to increased rates of resistance among conjunctival flora. Repeated use of topical fluoroquinolones after intravitreal injections may have a detrimental effect on eye health by breeding resistance in the bacterial flora.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Topical
  • Aged
  • Aged, 80 and over
  • Anti-Bacterial Agents / administration & dosage*
  • Aza Compounds / administration & dosage
  • Bacteria / drug effects
  • Bacteria / isolation & purification*
  • Case-Control Studies
  • Conjunctiva / microbiology*
  • Cross-Sectional Studies
  • Drug Resistance, Multiple, Bacterial*
  • Eye Infections, Bacterial / drug therapy
  • Eye Infections, Bacterial / microbiology*
  • Female
  • Fluoroquinolones
  • Humans
  • Intravitreal Injections
  • Macular Degeneration / drug therapy
  • Male
  • Microbial Sensitivity Tests
  • Middle Aged
  • Moxifloxacin
  • Ofloxacin / administration & dosage
  • Ophthalmic Solutions
  • Polymyxin B / administration & dosage
  • Quinolines / administration & dosage
  • Trimethoprim / administration & dosage


  • Anti-Bacterial Agents
  • Aza Compounds
  • Fluoroquinolones
  • Ophthalmic Solutions
  • Quinolines
  • Ofloxacin
  • Trimethoprim
  • Polymyxin B
  • Moxifloxacin