Topical antibiotic treatment effective in preventing endophthalmitis

November 1, 2006

Salt Lake City-Topical antibiotic therapy before and after intraocular bacterial challenge in rabbits could prevent Staphylococcus epidermidis endophthalmitis from developing.

Prophylaxis with a 3-mg/ml gatifloxacin (Zymar, Allergan) presoaked collagen shield was associated with lower rates of endophthalmitis if compared with prophylaxis with 5-mg/ml moxifloxacin (Vigamox, Alcon Laboratories) presoaked shields, Brian Haugen, MD, reported.

"Endophthalmitis is a devastating complication following surgery. The Moran Eye Center just published a reported indicating that 27 of 1,525 patients developed endophthalmitis over a 7-year period," Dr. Haugen said.

First the investigators needed to determine the minimal concentration of Sepidermidis that could induce clinical signs of endophthalmitis.

Group 1 of rabbits received 3 mg/ml gatifloxacin drops or the collagen shield soaked in 3 mg/ml gatifloxacin. Group 2 received gatifloxacin drops or a collagen shield soaked in 10 mg/ml of gatifloxacin (Tequin, Bristol-Myers Squibb). Group 3 animals were given 5 mg/ml moxifloxacin drops, or a shield soaked in 5-mg/ml moxifloxacin. Finally, Group 4, the control group, received balanced saline solution (BSS) drops or a shield soaked in BSS. Each eye received one drop of gatifloxacin, moxifloxacin, or BSS four times beginning 1 hour before the bacterial injection. Immediately after the injection, the collagen shield was placed in the eye randomly assigned to receive the shield.

The antibiotic drops were instilled once every 2 hours postoperatively for a total of five doses, according to Dr. Haugen. The animals in the gatifloxacin group received the 3-mg/ml gatifloxacin drops to determine if the collagen shield soaked in a higher concentration of gatifloxacin made a difference in the treatment results.

Signs of endophthalmitis

Twenty-four hours after the bacterial challenge, the animals were examined by slit lamp to determine the presence of the clinical signs of endophthalmitis. The different clinical parameters were scored by a scale ranging from 0 to 4, with 4 representing the presence of the worst clinical signs of endophthalmitis. Then, a total clinical score was noted for each eye.

"The reaction with the antibiotic-soaked shields in place was not as intense as in the control group. There was more cell and flare in the eyes with a moxifloxacin shield," Dr. Haugen stated.

He also reported that the main clinical scores for the shields were not significantly different from those of the topical drops alone.