Intravitreal injections of antibiotics and anti-inflammatories are used by some cataract surgeons for surgical prophylaxis. To support this prophylaxis, intravitreal triamcinolone–moxifloxacin (TM) and triamcinolone–moxifloxacin–vancomycin (TMV) were tested for preventing Staphylococcus aureus (SA) endophthalmitis in rabbits.Methods:
Trademark formulations of TM (15/1 mg/mL) and TMV (15/1/10 mg/mL) were intravitreally injected into seven groups of eight rabbits each (A–G). Before intravitreal injection, the vitreous was first challenged with clinical SA endophthalmitis isolates (5,000 colony-forming unit) with varying minimum inhibitory concentrations (MICs in μg/mL) to moxifloxacin (denoted by the MIC at the end of each group listed): A) TMV-10, B) TM-10, C) Saline-10, D) TM-2, E) Saline-2, F) TM-0.032, and G) Saline-0.032. After 24 hr, the rabbit eyes were graded for clinical endophthalmitis and cultured for viable SA.Results:
Rabbits treated with TMV and challenged by SA with a moxifloxacin MIC of 10 μg/mL did not present with endophthalmitis (0/8, no eyes with endophthalmitis). For SA with moxifloxacin MICs of 10.0 and 2.0 μg/mL, TM did not prevent endophthalmitis (16/16, 100% of eyes with endophthalmitis). For SA with a moxifloxacin MIC of 0.032 μg/mL, endophthalmitis was prevented with TM (0/8, no eyes with endophthalmitis). All saline-treated eyes developed endophthalmitis (23/23, 100% of eyes with endophthalmitis).Conclusions:
Intravitreal monotherapy with TM did not provide consistent prevention of SA endophthalmitis, whereas intravitreal TMV successfully prevented endophthalmitis because of SA with elevated MIC values to moxifloxacin. Cataract surgeons need to be aware that vancomycin seems to be essential for intravitreal prophylaxis to cover moxifloxacin resistance.