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J.C. Liu, J.M. Kurilec, G.W. Zaidman, P. Patel, J.N. Kruh, M.E. Aguero–Rosenfeld, K.B. Juechter; Determining the Optimal Treatment for Group B Streptococcal Keratitis: An Animal Model . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3557.
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Group B Streptococcus (GBS) is an uncommon yet devastating ocular microbial infection. We created an animal model of GBS keratitis to investigate the most effective topical antibiotic treatment.
A 3–stage experiment was designed. Stage 1 tested in–vitro sensitivity of GBS to gatifloxacin 0.3% (GAT), moxifloxacin 0.5% (MOX), ciprofloxacin 0.3% (CIP), sulfacetamide 10% (SULF), fortified vancomycin 50mg/ml (VANC), fortified cefazolin 50mg/ml (CEF), and balanced salt solution (BSS). Stage 2 involved a rabbit model where 14 corneas of 14 New Zealand white (NZW) rabbit eyes were inoculated with 103 CFU of GBS in 20µl of trypic soy broth (TSB). Following an incubation period of 7 hours, the rabbits where randomly divided into 5 groups and treated by some of the antibiotics from Stage 1 (CEF, MOX, GAT, and VANC) with BSS as the control. Rabbit eyes received topical treatment over 7 days with the schedule: q 15min x 1 hr, q 1 hr x 36 hrs, q 2 hrs x 72hrs, and q 6 hrs x 36 hrs. The eyes were evaluated daily on a score of 0 to 4+ regarding 5 parameters: discharge, conjunctival injection, corneal infiltrate, staining, and neovascularization. On day 7, the animals were euthanized and the eyes enucleated and sent for histo–pathologic examination. Using the same animal model, Stage 3 compared the 2 most favorable topical antibiotics from Stage 2 outcomes (CEF and MOX) and BSS as the control. 12 corneas of 12 NZW rabbit eyes were inoculated and treated with the same protocol as in Stage 2. The animals were euthanized and the eyes enucleated following 7 days of treatment.
In Stage 1, the in–vitro sensitivity of GBS was CEF > MOX > GAT > CIP > VANC and resistant to SULF and BSS. In Stage 2, all VANC treated eyes had significant discharge through day 5 and developed keratitis and central ulcers. Controls developed hypopyons and severe infiltrates with corneal neovascularization. Overall clinical efficacy was CEF = MOX > GAT > VANC > BSS. Stage 3 showed no clinical difference between MOX and CEF regarding discharge, staining, and neovascularization. By day 7, corneal infiltrates and injection cleared up slightly earlier in MOX vs. CEF, but both groups demonstrated almost complete resolution.
Based on our results we conclude that CEF and MOX are equivalent for the best treatment of GBS keratitis. Due to its readily available preparation we recommend MOX as the initial treatment of choice for GBS keratitis.
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