2001 Ocular Microbiology and Immunology Group, Abstract 13

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Effectiveness of Moxifloxacin and Quixin™ in a Rabbit Model of Staphylococcus Keratitis
R. O'Callaghan¹,², J. Dajcs1, M. Austin¹, D. Girgis¹, B. Thibodeaux¹, M. Trade¹ and D. Stroman^3
1LSU Health Sciences Center, ²LSU Eye Center, ³Alcon Research, LTD

Purpose: To compare the effectiveness of new fluoroquinolones for experimental Staphylococcus keratitis involving methicillin and ofloxacin sensitive (MSSA and ofloxS) or resistant (MRSA and ofloxR ) strains.

Methods: Rabbit corneas were intrastromally injected with approximately 100 colony forming units (CFU) of log phase culture S.aureus laboratory strain 8325-4 (MSSA, ofloxS) or clinical strains MRSA 301 (MRSA, ofloxS), 60171 (MSSA, ofloxR), or 30155 (MRSA, ofloxR). Rabbit corneas were treated with moxifloxacin (0.5% ophthalmic solution) or Quixin™ (0.5% levofloxacin ophthalmic solution) every 30 minutes beginning at 4 or 10 hours postinfection (PI) for five hours. Rabbits were sacrificed one hour after treatment ceased and corneas were excised and cultured to determine the CFU/cornea.

Results: Rabbit corneas infected with either MRSA 301 or 8325-4 and treated at 4-9 or 10-15 hours PI with moxifloxacin had <1.93 log CFU/cornea compared to approximately 6.8 log CFU/cornea of the untreated group (P<0.0001). Rabbit corneas infected with strain 60171 or 30155 and treated 4-9 hours PI with moxifloxacin or Quixin™ had approximately 1 and 2 logs CFU respectively (P< 0.0007), whereas the untreated eyes had 6 logs CFU (P<0.0001). Log CFU of rabbit corneas infected with strain 60171 and treated at 10-15 hours PI with moxifloxacin (6.03 + 0.17) but not Quixin™ (6.26 + 0.06) was significantly lower than the untreated group (6.65 + 0.14: P=0.0416). Rabbit corneas infected with strain 30155 and treated at 10-15 hours PI with moxifloxacin had 4.57 + 0.38 log CFU/cornea, which was significantly less than the CFU/cornea of the Quixin™ treated group (6.01 + 0.10; P<0.0001). Only moxifloxacin reduced the CFU/cornea compared to the untreated group (P<0.0001).

Conclusions: Moxifloxacin, as compared to Quixin™, was significantly more effective in treating both ciprofloxacin sensitive and ciprofloxacin -resistant experimental Staphylococcus aureus keratitis.

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