Introduction: Bacterial ulcerative keratitis is a serious condition that requires an early diagnosis as well as an immediate and adequate treatment. Staphylococcus aureus is the predominant pathogen isolated from the majority of cases of keratitis. In recent years, the emergence of methicillin-resistant Staphylococcus aureus (MRSA) strains has been observed in ocular infections. The resistance of MRSA also to second-and third-generation fluoroquinolones has increased the interest in the fourth-generation fluoroquinolones. The aim of this study was: (a) to monitor in vitro the susceptibility of ocular isolates versus gemifloxacin and others antibiotics; (b) to test the effectiveness of gemifloxacin 0.3% solution in an ex vivo model of MRSA-induced keratitis. Materials and Methods: In vitro susceptibility studies were performed on various strains of S. aureus ocular isolates (including MRSA) to determine the minimum inhibitory concentration (MIC) of gemifloxacin, ofloxacin, levofloxacin, ciprofloxacin, moxifloxacin and gentamicin using E-test method. MRSA-keratitis were performed using a modified ex vivo rabbit model. Corneal buttons with sclera rims, placed in colture, were intrastromally injected with 50 µl of the bacterial suspension (5 x 105 colony forming units/ml-CFU/ml) of each strain. Twenty hours after the injection (late treatment), 1 topical drop of gemifloxacin ophthalmic solution (0.3%) (treated group) and balanced salt solution (BSS) (untreated group ) was applied to each cornea every 30 min for 14 administration. The corneas were examined both before and after treatment. The tissues from treated and untreated samples were homogenized and serially plated to determine the number of recovered CFU/g. Results: In vitro susceptibility study findings indicated that the MIC of gemifloxacin was lower than the MIC of other fluoroquinolones and gentamicin. Experimental keratitis showed a statistically significant decrease (p<0.05) of MRSA (1 to 2 log10 CFU/g) in gemifloxacin-treated corneas. Discussion and conclusions: Topical gemifloxacin 0.3% may be effective for the treatment of MRSA-induced keratitis. Additionally, this reproducible, ethical and economic ex vivo model can be used as a mechanistically-based alternative to in vivo animal testing bridging the gap between in vitro and in vivo results.

Efficacy of gemifloxacin in ex vivo experimental keratitis due to methicillin-resistant Staphylococcus aureus

MARINO, Andreana;GINESTRA, GIOVANNA;NOSTRO, Antonia;BISIGNANO, Giuseppe Giov.
2015-01-01

Abstract

Introduction: Bacterial ulcerative keratitis is a serious condition that requires an early diagnosis as well as an immediate and adequate treatment. Staphylococcus aureus is the predominant pathogen isolated from the majority of cases of keratitis. In recent years, the emergence of methicillin-resistant Staphylococcus aureus (MRSA) strains has been observed in ocular infections. The resistance of MRSA also to second-and third-generation fluoroquinolones has increased the interest in the fourth-generation fluoroquinolones. The aim of this study was: (a) to monitor in vitro the susceptibility of ocular isolates versus gemifloxacin and others antibiotics; (b) to test the effectiveness of gemifloxacin 0.3% solution in an ex vivo model of MRSA-induced keratitis. Materials and Methods: In vitro susceptibility studies were performed on various strains of S. aureus ocular isolates (including MRSA) to determine the minimum inhibitory concentration (MIC) of gemifloxacin, ofloxacin, levofloxacin, ciprofloxacin, moxifloxacin and gentamicin using E-test method. MRSA-keratitis were performed using a modified ex vivo rabbit model. Corneal buttons with sclera rims, placed in colture, were intrastromally injected with 50 µl of the bacterial suspension (5 x 105 colony forming units/ml-CFU/ml) of each strain. Twenty hours after the injection (late treatment), 1 topical drop of gemifloxacin ophthalmic solution (0.3%) (treated group) and balanced salt solution (BSS) (untreated group ) was applied to each cornea every 30 min for 14 administration. The corneas were examined both before and after treatment. The tissues from treated and untreated samples were homogenized and serially plated to determine the number of recovered CFU/g. Results: In vitro susceptibility study findings indicated that the MIC of gemifloxacin was lower than the MIC of other fluoroquinolones and gentamicin. Experimental keratitis showed a statistically significant decrease (p<0.05) of MRSA (1 to 2 log10 CFU/g) in gemifloxacin-treated corneas. Discussion and conclusions: Topical gemifloxacin 0.3% may be effective for the treatment of MRSA-induced keratitis. Additionally, this reproducible, ethical and economic ex vivo model can be used as a mechanistically-based alternative to in vivo animal testing bridging the gap between in vitro and in vivo results.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/3065423
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