Fluoroquinolone therapy in a rabbit model of post-LASIK methicillin-resistant Staphylococcus aureus keratitis

A methacrylated hyaluronic acid network reinforced Pluronic F-127 gel for treatment of bacterial keratitis

In this study, we developed a novel in situ thermoresponsive gel by introducing crosslinked methacrylated hyaluronic acid (HA-MA) networks into Pluronic F-127 (PF-127) gel (HP gel) to achieve levofloxacin (LFX) delivery in bacterial keratitis treatment. The interactions between PF-127 and HA-MA networks were studied by scanning electron microscopy, rheology, dynamic light scattering, differential scanning calorimetry, and small angle X-ray scattering. The results showed that the HP gel exhibited a higher critical gelling temperature and lower viscosity than the PF-127 gel (P gel), and could form a uniform thin layer on the ocular surface. Moreover, the drug release profile and gel dissolution rate revealed that the HA-MA network could retard the diffusion and dissolution of drug molecules and prolong the drug release time, which corresponded to an enhanced antibacterial ability of the HP-LFX gel. Furthermore, the HP gel exhibited low cytotoxicity to human corneal epithelial cells (HCECs). Finally, an in vivo pharmacodynamic study was conducted with rabbit keratitis models. An improved treatment efficacy was observed after application of the HP-LFX gels. This study highlights the potential of HP gels in ophthalmic drug delivery.

Eye drops and eye gels of levofloxacin: comparison of ocular absorption characterizations and therapeutic effects in the treatment of bacterial keratitis in rabbits

The aim was to reveal the characteristic profiles of the marketed levofloxacin eye drops (5 mg/ml) and levofloxacin eye gel (3 mg/g) from the pharmacokinetics and pharmacodynamics views of rabbits' eyes. A mild and a heavy bacterial keratitis models in rabbits were established. Different regimens of levofloxacin eye drops and eye gel, including phosphate buffer solution (the PBS group), the 4-Sol + 1-Gel group (rabbits were treated with 4 doses of levofloxacin eye drops and 1 dose levofloxacin eye gel per day), the 3-Sol + 1-Gel group (3 doses drops and 1 dose gel), the 4-Sol group (4 doses drops), the 4-Gel group (4 doses gel), the 3-Sol group (3 doses drops), and the 3-Gel group (3 doses gel), were applied to evaluate their efficacies. The ocular pharmacokinetics of levofloxacin eye drops and gel were also investigated. The results of mild infection groups showed that all treatment regimens significantly relieved the infection symptoms, and the treatment effect followed this order: 4-Gel > 4-Sol + 1-Gel > 3-Sol + 1-Gel > 4-Sol > 3-Gel > 3-Sol. In the heavy infection groups, all the treatment regimens significantly relieved the infection symptoms, and the treatment effect also followed the order with the mild infection results. All treatment regimens lowered the number of corneal colony forming units (CFU). Levofloxacin eye gel significantly increased intraocular penetration in rabbits' eyes. It can be concluded that the levofloxacin eye gel was more effective in treating bacterial keratitis than the levofloxacin eye drops in rabbit keratitis model with a proper treatment regimen such as 4-Gel.

Normal corneal thickness measurements in pigmented rabbits using spectral-domain anterior segment optical coherence tomography

OBJECTIVE

To document the thickness of the central cornea in pigmented rabbits using spectral-domain anterior segment optical coherence tomography (AS-OCT).

ANIMALS STUDIED

Seventeen pigmented rabbits (6 male, 11 female, both eyes) were involved in this study.

PROCEDURES

Thirty-four eyes from healthy pigmented rabbits underwent a complete ophthalmologic examination, including AS-OCT. Eight radial scans, 6 mm in length and centered on the cornea, were obtained using the AS-OCT. Corneal thickness was automatically calculated using pachymetry software. Measurements were displayed as the mean and standard deviation for each of the 17 regions defined by the software. The regions were the center (1 mm radius, area a), the inner ring (2.5 mm radius, area b), the outer ring (3 mm radius, area c), and the eight radial scan lines in eight directions (Superior (1), SN (2), Nasal (3), IN (4), Inferior (5), IT (6), Temporal (7), ST (8)) with an angle of 45° between each consecutive scan line (a, b 1-8, c 1-8).

RESULTS

There was no statistically significance difference in corneal thickness between gender, eye, and the eight directions (P = 0.804, P > 0.05, P > 0.05). There was a statistical difference between the thickness in areas a, b, and c (P < 0.05). The corneal thickness increased gradually from the center to the periphery of the 6 mm measured. The center corneal thickness was 387 ± 19.8 μm for OD and 384 ± 20.2 μm for OS. The corneal thicknesses of the thinnest point of the right eyes (OD) and the left eyes (OS) were 376 ± 20.2 and 370 ± 16.8 μm, respectively. There was positive correlation between the thinnest point and area a in both the right eyes (r = 0.892, P < 0.001) and the left eyes (r = 0.832, P < 0.001).

CONCLUSIONS

This is the first documentation of the rabbit corneal thickness in vivo using the spectral-domain AS-OCT. Pigmented rabbit corneas were almost 150 μm thinner than human corneal values. Gender and eye were not associated with any statistical differences in central corneal thickness in this study.

Animal models of bacterial keratitis

Bacterial keratitis is a disease of the cornea characterized by pain, redness, inflammation, and opacity. Common causes of this disease are Pseudomonas aeruginosa and Staphylococcus aureus. Animal models of keratitis have been used to elucidate both the bacterial factors and the host inflammatory response involved in the disease. Reviewed herein are animal models of bacterial keratitis and some of the key findings in the last several decades.

Secretory Leukoprotease Inhibitor: A Native Antimicrobial Protein in the Innate Immune Response in a Rat Model of S. aureus Keratitis

Purpose. To describe the presence of secretory leukocyte protease inhibitor (SLPI), a cationic peptide with antimicrobial and antiprotease activity in the innate immune reaction in a rat model of Staphylococcus aureus keratitis. Methods. Forty female Lewis rats were divided into 2 groups: the infectious keratitis and the epithelial defect groups. Eyes were processed for immunohistochemical studies for SLPI, interleukin-1, interleukin-6, tumor necrosis factor-alpha, and matrix metalloproteinase-8. Results. Immunohistochemical studies confirmed high levels of SLPI, IL-1, IL-6, TNF-α, and MMP-8 expression in eyes with S. aureus keratitis and with epithelial defects, in contrast to undetectable SLPI expression in the normal control corneas. Conclusions. To our knowledge, this paper is the first to demonstrate the presence of SLPI with increased amounts of proinflammatory cytokines in inflamed and infected corneas.