In vitro toxicity of netilmicin and ofloxacin on corneal epithelial cells

Drug-Related Keratitis: A Real-World FDA Adverse Event Reporting System Database Study

Purpose

This study aimed to assess the drug risk of drug-related keratitis and track the epidemiological characteristics of drug-related keratitis.

Methods

This study analyzed data from the U.S. Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) database from January 2004 to December 2023. A disproportionality analysis was conducted to assess drug-related keratitis with positive signals, and drugs were classified and assessed with regard to their drug-induced timing and risk of drug-related keratitis.

Results

A total of 1606 drugs were reported to pose a risk of drug-related keratitis in the FAERS database, and, after disproportionality analysis and screening, 17 drugs were found to significantly increase the risk of drug-related keratitis. Among them, seven were ophthalmic medications, including dorzolamide (reporting odds ratio [ROR] = 3695.82), travoprost (ROR = 2287.27), and brimonidine (ROR = 2118.52), and 10 were non-ophthalmic medications, including tralokinumab (ROR = 2609.12), trazodone (ROR = 2377.07), and belantamab mafodotin (ROR = 680.28). The top three drugs having the highest risk of drug-related keratitis were dorzolamide (Bayesian confidence propagation neural network [BCPNN] = 11.71), trazodone (BCPNN = 11.11), and tralokinumab (BCPNN = 11.08). The drug-induced times for non-ophthalmic medications were significantly shorter than those for ophthalmic medications (mean days, 141.02 vs. 321.96, respectively; P < 0.001). The incidence of drug-related keratitis reached its peak in 2023.

Conclusions

Prevention of drug-related keratitis is more important than treatment. Identifying the specific risks and timing of drug-induced keratitis can support the development of preventive measures.

Translational Relevance

Identifying the specific drugs related to medication-related keratitis is of significant importance for drug vigilance in the occurrence of drug-related keratitis.

Clinical features and comprehensive treatment of persistent corneal epithelial dysfunction after cataract surgery

OBJECTIVE

Evaluation of clinical efficacy and safety of tobramycin/dexamethasone eye ointment in treating persistent corneal epithelial dysfunction (PED) after cataract surgery.

METHODS

26 cases diagnosed as PED after cataract surgery accept the tobramycin/dexamethasone ophthalmic ointment and intense pulse light treatment in the Xiamen University of Xiamen eye center between September 2016 and April 2022 were retrospectively analyzed, mainly including clinical manifestations, characteristics of morphological changes imaged by in vivo confocal microscopy, meibomian glands infrared photography, lipid layer thickness (LLT), management and therapeutic effects.

RESULTS

There were 26 eyes, include 8(35%) males and 15(65%) females with an average age of 69.6 ± 5.2 years(50 to 78 years). The mean hospitalization time was (18.4 ± 7.5) days after cataract surgery. Twenty patients had meibomian gland dysfunction. Infrared photography revealed varying loss in the meibomian glands, with a mean score of 3.8 ± 1.2 for gland loss. The mean LLT was 61.6 ± 8.4 nm. After treatment, 20 patients were cured, and 3 received amniotic membrane transplantation. After treatment, the uncorrected visual acuity (UCVA) and best-corrected vision activity (BCVA) improved (P < 0.001), and there was no significant difference in intraocular pressure (IOP) before and after treatment (P > 0.05).

CONCLUSIONS

The early manifestation of PED after surgery is punctate staining of the corneal epithelium. Tobramycin and dexamethasone eye ointment bandages have a good repair effect. The meibomian gland massage combined with intense pulse light treatment can effectively shorten the course of the disease.

Ocular topical application of alpha-glucosyl hesperidin as an active pharmaceutical excipient: in vitro and in vivo experimental evaluation

Alpha-glucosyl hesperidin (GH) is an aqueous soluble, amphipathic hesperidin derivative with several pharmacological effects, and it is postulated in this manuscript that GH could potentially be utilized as an active pharmaceutical excipient in eyedrops. The ocular safety of GH was evaluated according to in vitro cytotoxicity and in vivo ocular tolerance. The in vivo corneal permeation of coumarin-6 (Cou-6) with or without GH was characterized, and the in vivo inducing corneal wound healing using bisdemethoxycurcumin (BDMC) with or without GH was also evaluated to determine whether GH is an active pharmaceutical excipient in eyedrops. The results demonstrated that as high as 30 mg/ml of GH exhibits high-level in vitro and in vivo safety profiles according to four in vitro and in vivo evaluations. GH improved the corneal permeation of Cou-6 in mice, as well as demonstrated in vitro antioxidant activity. Concerning in vivo activity, a BDMC-GH suspension was shown to be synergistic in promoting corneal wound healing in mice, as well as restoring corneal sensitivity, promoting corneal epithelial wound healing, and restoring the corneal tissue structure without inflammatory cell infiltration. Overall, GH could be a novel and promising active excipient in eyedrops.

In Vitro and Ex Vivo Models for Assessing Drug Permeation across the Cornea

Drug permeation across the cornea remains a major challenge due to its unique and complex anatomy and physiology. Static barriers such as the different layers of the cornea, as well as dynamic aspects such as the constant renewal of the tear film and the presence of the mucin layer together with efflux pumps, all present unique challenges for effective ophthalmic drug delivery. To overcome some of the current ophthalmic drug limitations, the identification and testing of novel drug formulations such as liposomes, nanoemulsions, and nanoparticles began to be considered and widely explored. In the early stages of corneal drug development reliable in vitro and ex vivo alternatives, are required, to be in line with the principles of the 3Rs (Replacement, Reduction, and Refinement), with such methods being in addition faster and more ethical alternatives to in vivo studies. The ocular field remains limited to a handful of predictive models for ophthalmic drug permeation. In vitro cell culture models are increasingly used when it comes to transcorneal permeation studies. Ex vivo models using excised animal tissue such as porcine eyes are the model of choice to study corneal permeation and promising advancements have been reported over the years. Interspecies characteristics must be considered in detail when using such models. This review updates the current knowledge about in vitro and ex vivo corneal permeability models and evaluates their advantages and limitations.

Aloe vera and ofloxacin incorporated chitosan hydrogels show antibacterial activity, stimulate angiogenesis and accelerate wound healing in full thickness rat model

Burns are potentially fatal and physically debilitating injuries, causing psychological and physical scars and result in chronic disabilities. A well vascularized wound bed is required to achieve complete and scar free wound closure. For many centuries, a variety of herbal plants have been used for wound healing, among these aloe vera (AV) has been found to be very effective in wound healing. Secondly, the main reason for delayed wound healing is bacterial infections. Ofloxacin (OX) has been reported as an active antibacterial drug for topical infections and it is effective against both positive and negative bacterial strains. In current research three different concentrations of OX (0.5, 2.5, and 5 mg) were loaded into chitosan (CS)/AV based hydrogels prepared by freeze gelation. The surface morphology of prepared CS/AV based OX loaded hydrogels were evaluated by scanning electron microscopy (SEM). In drug release analysis, 0.5 mg OX loaded hydrogel showed a sustained drug release behavior over 3 days period. An effective dose dependent antibacterial activity was exhibited by OX loaded hydrogels. Alamar Blue cells viability assay revealed that 0.5 mg OX hydrogel (CA 0.5 OX) showed comparatively better 3 T3 fibroblast cells proliferation as compared to CA 2.5 OX (2.5 mg OX) and CA 5 OX hydrogel (5 mg OX). Moreover, all OX loaded hydrogels showed good angiogenic activity in CAM bioassay while higher angiogenic potential was observed from CA 0.5 OX containing comparatively lower concentration of OX. These OX incorporated CS/AV based hydrogels are promising wound dressings for future clinical use.

Characteristics of Toxic Keratopathy, an In Vivo Confocal Microscopy Study

Purpose

Toxic keratopathy (TK) involves complex clinical manifestations and is difficult to differentiate from other ocular surface diseases by conventional slit-lamp examination. The challenge faced by clinicians in confidently diagnosing TK cannot be underestimated. This study aimed to explore the microstructural characteristics and diagnostic parameters by in vivo confocal microscopy (IVCM) in TK.

Methods

In this prospective, cross-sectional, comparative study, slit-lamp and IVCM examinations were performed on 20 normal eyes and 54 eyes with TK. Based on slit-lamp imaging, TK subjects were divided into four groups: superficial punctate keratitis (n = 10 eyes), pseudodendritic keratitis (n = 14 eyes), ulcerative keratitis (UK; n = 16 eyes), and ring keratitis (RK; n = 14 eyes). The microstructural characteristics of TK were described according to the following IVCM parameters: basal cell (BC) density, dendritiform cell (DC) density, DC size, corneal nerve fiber (CNF) length, nerve tortuosity, and keratocyte reflectivity. A receiver operating characteristic (ROC) curve model was also formulated to compare the predictive power of BC density, DC density, and CNF length.

Results

TK eyes showed significantly higher values for DC density (45.8 cells/mm²; range, 25.0–100.0) compared with normal eyes (24.0 cells/mm²; range, 20.8–32.3; P = 0.013; DC size (111.0 µm²; range, 92.0–137.8) compared with normal eyes (63.7 µm²; range, 47.7–70.3; P < 0.001); nerve tortuosity (0.08; range, 0.05–0.09) compared with normal eyes (0.04; range, 0.02–0.04; P < 0.001); and keratocyte reflectivity. BC density and CNF length values were found to be significantly less than those for normal controls (both P < 0.001). In all subgroups, CNF length appeared to be significantly lower than that of controls (all P < 0.001), and DC density was only statistically significantly higher in the UK (P = 0.003) and RK (P < 0.001) groups. Corneal fluorescein staining had no correlation with the analyzed IVCM parameters (all P ˃ 0.05). However, the increase in DC density and DC size showed negative correlations to CNF length (density: r = −0.325, P < 0.005; size: r = −0.493, P < 0.005), as well as positive correlations to duration and frequency of topical eye drops and DC size (density: r = 0.361, P < 0.05; size: r = 0.581, P < 0.05). A ROC curve showed that CNF length had the strongest predictive power, with the estimated area under the curve being 0.992 ± 0.008.

Conclusions

Lower BC density and CNF length, greater DC density and DC size, and greater keratocyte reflectivity were the microstructural characteristics of TK. The role of subbasal nerve, inflammatory response, and limbal stem cells in the progression of TK and the appropriate treatment of different TK stages are future research directions.

Translational Relevance

The evaluation of basal cells, subbasal nerve, and dendritiform cells is helpful to our understanding of the pathological process of TK.

Effects of topical Coenzyme Q10, Xanthan Gum and Sodium Hyaluronate on corneal epithelial wound healing

Clinical Relevance: Effective treatment of corneal epithelial defects is crucial to prevent secondary infectious keratitis and visual impairment due to loss of corneal transparency. Therefore, it is important to determine the effect of different topical agents on corneal wound healing response.Background: The aim was to compare the effects of three different eye drops on corneal epithelial wound healing in an experimental model.Methods: Twenty-four eyes of 24 female BALB/c mice were included. A 2 mm central corneal epithelial defect was created. Topical Coenzyme Q10 + Vitamin E D-α-TPGS 4 × 1 was applied to Group A (n = 6), topical Sodium hyaluronate + Xanthan Gum + 0.3% Nethylmicine 4 × 1 to Group B (n = 6) and topical Sodium hyaluronate 4 × 1 to Group C (n = 6). Group D (n = 6) was the control group without treatment. Clinical scoring according to corneal fluorescein staining and histopathological evaluations was performed.Results: Clinical scores according to corneal fluorescein staining were similar in all groups on days 1 (p = 0.05), 2 (p = 0.15) and 3 (p = 0.62). Electron microscopy revealed disruption of intercellular junctions between corneal epithelial cells and intracellular vacuole formation in all groups except Group A. Corneal epithelial thickness and superficial epithelial microvillus arrangement were close to normal in Group A.Conclusion: Although there was no difference in clinical scores between groups, electron microscopy revealed a better organised epithelium with normal configuration of microvilli and less vacuolisation in Group A.

Combined eye gel containing sodium hyaluronate and xanthan gum for the treatment of the corneal epithelial defect after pterygium surgery

Aim

The aim of this study is to compare the effectiveness of the ophthalmic gels containing hyaluronate, xanthan gum, and netilmycine with fusidic acid in terms of recovery periods of corneal epithelium in the patients who underwent pterygium surgery.

Methods

Patients who underwent pterygium surgery were separated into two groups. Forty patients in group 1 were given eye gel containing sodium hyaluronate, xanthan gum, and netilmycine, and 40 patients in group 2 were given one drop of eye gel containing fusidic acid. The patients in both groups were examined at the 12th, 24th, and 48th hours in the postoperative period by using slit-lamp technique. The subjective complaints of the patients such as pain and stinging, and the recovery periods of the corneal epithelial defect were evaluated comparatively by fluorescein staining.

Results

The mean ages were 26±8 years (range: 18–35) and 24±6 years (range: 18–33) in groups 1 and 2, respectively. The closure period of the corneal epithelial defect was observed as 24±8 hours (range: 16–42) and 36±12 hours (range: 18–48) in groups 1 and 2, respectively. The number of the patients suffering from subjective complaints such as pain and stinging in the first 12 hours was six and 29 in groups 1 and 2, respectively. The difference was significant both clinically and statistically (P=0.001).

Conclusion

Combined eye gel containing hyaluronate, xanthan gum, and netilmycine accelerates the recovery of corneal epithelial defect and reduces the complaints of the patients, when compared to the fusidic acid gel. Combined eye gel should be considered as an option for the treatment of the corneal epithelial defect related with pterygium surgery.

A new eye gel containing sodium hyaluronate and xanthan gum for the management of post-traumatic corneal abrasions

PURPOSE

The aim of this study was to investigate the effects of an ophthalmic gel containing sodium hyaluronate and xanthan gum in addition to the antibiotic netilmicin in the management of traumatic corneal abrasions.

PATIENTS AND METHODS

PATIENTS WITH TRAUMATIC CORNEAL ABRASIONS WERE RANDOMLY TREATED AS FOLLOWS: Group A (n = 20) with an occlusive patching for 12 hours plus one drop of an eye gel containing 0.15% sodium hyaluronate, 1% xanthan gum and 0.3% netilmicin qid for 5 days; and Group B (n = 20) with an occlusive patching for 2-3 days plus one application of 0.3% netilmicin ophthalmic ointment qid for 5 days. All patients were evaluated after the third and seventh day by slit-lamp examination, fluorescein staining, and corneal defect photograph in order to assess corneal re-epithelialization. Conjunctival hyperaemia, lid oedema, subjective symptoms of discomfort, and conjunctival swabs were also evaluated.

RESULTS

No statistically significant difference was observed between the groups in terms of the extent of corneal healing after 3 days of treatment. Both treatments were also highly effective in decreasing the erosion score and the conjunctival hyperemia (P < 0.0001, P < 0.005, respectively) without any significant difference between the two types of treatment. Subjective symptoms of discomfort and conjunctival swabs were also evaluated.

CONCLUSION

In the management of traumatic corneal abrasions, the administration of an eye gel containing sodium hyaluronate and xanthan gum is able to reduce the length of occlusive patching. In addition, the presence of netilmicin guarantees good antibiotic prophylaxis during the wound repair process.

Comparison of moxifloxacin and levofloxacin in an epithelial disorder model using cultured rabbit corneal epithelial cell sheets

BACKGROUND

When ophthalmic drug solutions are developed and clinically applied, their influence on corneal epithelium is an important issue. In the past, cells obtained by monolayer culture in vitro were used for evaluation of such influence. We recently created an experimental model of cell damage repair closer to the live body than conventional models by using layered sheets of cultured corneal epithelium. The present study was undertaken to evaluate the influence of ophthalmic moxifloxacin hydrochloride (MFLX) solution in comparison to that of ophthalmic levofloxacin (LVFX) solution using this model.

METHODS

Corneal epithelium cells were collected from corneal tissue specimens of white rabbits and subjected to air-lift culture to induce layering. Epithelial cell defects were created by a sponge soaked in 1 N aqueous sodium hydroxide. After removal of the sponge, either ophthalmic MFLX solution or ophthalmic LVFX solution was dropped onto the specimens three times daily (washed 1 min after each dose, followed by continuation of air-lifting culture). The percentage of the defective area repaired (percent defect repair) was evaluated. Each of the ophthalmic MFLX solution and the ophthalmic LVFX solution was used after the stock solution was diluted fourfold (1:4). Drug-free culture medium served as the negative control. Benzalconium chloride solution (BAC) 0.01% served as the positive control.

RESULTS

In the negative control group, complete repair of the defect with epithelial cells was seen 4 days after the start of treatment. In the positive control group, repair was suppressed. In the MFLX group and the LVFX group, the defect was repaired at each drug concentration, showing no significant difference from the negative control group. Thus, in this study using layered sheets of cultured corneal epithelium (a model closer to the living body than conventional models), the corneal epithelial defect was repaired in the ophthalmic MFLX solution treatment group and the ophthalmic LVFX solution treatment group to a degree similar to that in the negative control group.

CONCLUSIONS

These results suggest that neither MLFX nor LVFX suppresses repair of corneal epithelial damage.

Magnetic luminescent porous silicon microparticles for localized delivery of molecular drug payloads

Magnetic manipulation, fluorescent tracking, and localized delivery of a drug payload to cancer cells in vitro is demonstrated, using nanostructured porous silicon microparticles as a carrier. The multifunctional microparticles are prepared by electrochemical porosification of a silicon wafer in a hydrofluoric acid-containing electrolyte, followed by removal and fracture of the porous layer into particles using ultrasound. The intrinsically luminescent particles are loaded with superparamagnetic iron oxide nanoparticles and the anti-cancer drug doxorubicin. The drug-containing particles are delivered to human cervical cancer (HeLa) cells in vitro, under the guidance of a magnetic field. The high concentration of particles in the proximity of the magnetic field results in a high concentration of drug being released in that region of the Petri dish, and localized cell death is confirmed by cellular viability assay (Calcein AM).

Corneal deposit of ciprofloxacin after laser assisted subepithelial keratomileusis procedure: a case report

Purpose. To report one case of corneal antibiotic deposition after ciprofloxacin administration in Laser Assisted Subepithelial Keratomileusis (LASEK). Methods. One case of post-LASEK treatment resulted in corneal precipitates and poor wound healing. Debris was analyzed with dark field microscopy and placed on a blood-agar plate seeded with a susceptible stain of Staphylococcus aureus (ATCC 29213). Results. The alterations resolved with discontinuation of ciprofloxacin treatment, although some residual deposits persisted subepithelially for 6 months. Analysis of precipitates revealed polydisperse crystalline needles of 183 μm average length (SD = 54 μm) and the excised precipitate demonstrated a zone of inhibition. Conclusions. Fluoroquinolone antibiotic drops have been used extensively in postsurgical treatment of refractive surgery. Corneal precipitates have been previously reported in the literature, but up to now nothing has been documented after LASEK. Polypharmacy during refractive surgery may impair epithelialisation, and clinical management should reduce toxic environment and promote ocular surface stability when performing surface ablations.

Comparison of fluoroquinolones: cytotoxicity on human corneal epithelial cells

PURPOSE

To compare the cytotoxicity of different fluoroquinolones (FQs) towards human corneal epithelial cells (HCECs).

METHODS

HCECs were incubated with FQs (norfloxacin, ciprofloxacin, ofloxacin, levofloxacin, moxifloxacin, and gatifloxacin), both as commercial ophthalmic formulations and as unpreserved solutions. Cells incubated in different formulations of gentamicin, cefazolin, and benzalkonium chloride (BAC) were also compared. A cell viability assay, using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay, was used to evaluate the drug effects on cell viability after five incubation times (30 min, 1 h, 4 h, 8 h, and 24 h). Transepithelial electrical resistance (TEER) was measured with a voltohmmeter to help understand changes in paracellular permeability at five time points (4 h, 8 h, 12 h, 24 h, and 48 h). Cell morphology was observed with an inverted fluorescence microscope, with multiple stage position and in time-lapse mode.

RESULTS

The preserving solutions and BAC at concentrations above 0.005% significantly decreased cell viability, when assayed by MTS. Increased paracellular permeability and decreased membrane integrity were also observed by TEER measurements and inverted fluorescence microscopy. Ofloxacin and levofloxacin were both free of preservatives and showed the least cytotoxicity towards HCECs in commercial FQ eye drops.

CONCLUSIONS

The cytotoxicity observed with FQ eye drops seems to be caused mainly by the preservative, which induced a significant decrease in membrane integrity and increased paracellular permeability. We found the new generation of FQs (moxifloxacin and gatifloxacin) no less cytotoxic towards HCECs than the old generation ones.

Corneal epithelial cell cultures as a tool for research, drug screening and testing

Understanding of visual system function and the development of new therapies for corneal diseases and damages depend upon comprehension of the biological roles of the tissue. The in vitro cultivation of corneal epithelial cells and cell lines derived from them has become a powerful tool to analyze and understand such issues. Currently, researchers have developed well-defined and precisely described culture protocols and a collection of corneal epithelial cell lines. These cell lines have been obtained through different experimental approaches: (1) the ectopic expression of oncogenes, (2) the inactivation of p16 and p53 pathways and hTERT expression, and (3) the spontaneous establishment after serial cultivation of cells. The advantages or disadvantages for these approaches are discussed. In conclusion, the availability of several culture protocols and immortalized cell lines that express corneal epithelial phenotype will be useful for investigating issues such as gene regulation and tissue development, or for validating alternative methods in toxicology.

Ocular toxicity of fluoroquinolones

The ocular toxicity of fluoroquinolones and the risks of their use in the treatment of ocular infection were reviewed. Systematic identification, selection, review and synthesis of published English-language studies relating to fluoroquinolone use and safety in animals and humans was conducted. Although not free of complications, fluoroquinolones are generally safe when used to treat ocular infection. Ocular toxicity appears to be dose-dependent and results from class-effects and specific fluoroquinolone structures. Phototoxicity and neurotoxicity have been reported, and toxic effects on ocular collagen may be associated with Achilles tendinopathy. Corneal precipitation may provide an advantageous drug depot but delay healing and result in corneal perforation in approximately 10% of cases. Although human toxicity studies are limited, the current recommended dose for intracameral injection of ciprofloxacin is less than 25 microg. Intravitreal injections of ciprofloxacin 100 microg, ofloxacin 50 microg/mL, trovafloxacin 25 microg or less, moxifloxacin 160 microg/0.1 mL or less and pefloxacin 200 microg/0.1 mL are considered safe.

Mechanism of L-ascorbic acid uptake by rabbit corneal epithelial cells: evidence for the involvement of sodium-dependent vitamin C transporter 2

PURPOSE

To investigate the mechanism of L-ascorbic acid uptake by rabbit corneal epithelial cells and to functionally characterize the specific transporter involved in this translocation process.

METHODS

Uptake studies were carried out with SIRC (Statens Seruminstitut Rabbit Cornea) and rPCEC (rabbit Primary corneal epithelial cell culture) in 12-well plates using [14C] Ascorbic acid (AA). Uptake was done in the presence of L-ascorbic acid and D-isoascorbic acid to delineate stereospecificity. Inhibition studies were performed in the presence of D-glucose a substrate for GLUT and also para amino hippuric acid (PAHA) a substrate for organic anion transporter. Effects of pH and sodium on the uptake of AA were characterized. Concentration dependency studies were performed. Energy dependence of AA uptake was investigated with ouabain and sodium azide in rPCEC. Reverse Transcription-polymerase chain reaction (RT-PCR) was also performed.

RESULTS

Uptake of AA was inhibited by about 90% and 50% respectively in the presence of L-ascorbic acid and D-isoascorbic acid in both SIRC and rPCEC. Uptake was unaltered by D-glucose and PAHA. The process was sodium dependent and saturable at higher concentrations. Ouabain and sodium azide significantly diminished the uptake process. It also decreased with a reduction in pH. The RT-PCR results showed the presence of SVCT2 but not SVCT1.

CONCLUSIONS

Uptake of AA across rabbit corneal epithelial cells appears to be a carrier mediated active process. A saturable, sodium dependent, and pH sensitive transporter with high specificity for L-ascorbic acid was functionally characterized and was identified as SVCT2.

Antimicrobial activity of antibiotic-treated amniotic membrane: An in vitro study

PURPOSE

To investigate if amniotic membrane incubated with antibiotics could inhibit bacterial growth in vitro.

METHODS

Amniotic membrane fragments were incubated with the antibiotics (netilmicin) solution; the washed and drained fragments were either tested after treatment or further incubated in antibiotic-free medium. The antibacterial activity of both amniotic membrane and elution media was carried out by the Agar diffusion method, with Staphylococcus epidermidis as indicator, measuring the inhibition zone after overnight incubation.

RESULTS

The amniotic membrane fragments soaked in antibiotics inhibited bacterial growth. Antibiotic uptake was dose-dependent and occurred rapidly. The drug was released from the membrane, and the antibacterial effect was present in the elution media at least 3 days after treatment.

CONCLUSIONS

Our preliminary in vitro data show that amniotic membrane can absorb the antibiotic netilmicin and in the future may be used to deliver antibiotics, as reported for collagen shields and other medical prosthetic devices.

Corneal deposits and topical ofloxacin—the effect of polypharmacy in the management of microbial keratitis

PURPOSE

To report six cases of corneal deposits after administration of topical ofloxacin in the treatment of bacterial keratitis.

METHOD/RESULT

Six cases of microbial keratitis treated with multiple topical medications, including topical ofloxacin, resulted in corneal precipitates and poor wound healing. In five cases, the precipitates resolved with discontinuation of ofloxacin treatment. However, in one patient, some residual deposits persisted following discontinuation of ofloxacin. The cornea epithelialised, but deposits were identified subepithelially.

DISCUSSION

Fluoroquinolone antibiotic drops have been extensively used in bacterial keratitis because of their ease of availability, broad spectrum of activity, and lack of toxicity. While corneal precipitates have been reported with cases of topical ciprofloxacin and norfloxacin, little has been documented on corneal deposits and topical ofloxacin in the treatment of bacterial keratitis. The predisposing factors resulting in corneal deposits and the role of polypharmacy are important features that may impair epithelialisation. Clinical management should be aimed at reducing the toxic environment and promoting ocular surface stability.

In Vitro Effects of Fluoroquinolone and Aminoglycoside Antibiotics on Human Keratocytes

PURPOSE

The purpose of this study was to assess the cytotoxic effects of the fluoquinolone ofloxacin and the aminoglycoside netilmicin on stromal human keratocytes in vitro.

METHODS

Cultured human keratocytes were exposed to various concentrations of ofloxacin or netilmicin (0.16-5.0 mg/mL). Both cell proliferation (MTT assay) and cell morphology (phase-contrast microscopy) were evaluated after 1, 4, 12, and 24 hours of incubation. Measurement of annexin V binding performed in association with the dye exclusion test using propidium iodide (PI) was also performed by FACS analysis after 4 hours of exposure.

RESULTS

Both antimicrobials induced dose- and time-dependent morphologic changes in keratocytes, yet the effects of netilmicin were minimal. After 24 hours of exposure, both drugs induced a dose-dependent inhibition of cell proliferation; however, ofloxacin demonstrated significantly more toxic effects than netilmicin (t test for ED50 values, P < 0.0001). Statistical differences between 2 antibiotics start at concentrations above 1.25 mg/mL (ANOVA with post-hoc test, P < 0.01). Expression of the apoptotic marker annexin V was unaffected by antibiotic exposure, whereas the uptake of the necrotic marker PI was increased by ofloxacin (5 mg/mL) but not by netilmicin (ofloxacin versus netilmicin, ANOVA, P < 0.05).

CONCLUSIONS

Relative effects of aminoglycosides and fluoroquinolones on stromal keratocytes appear to be different: netilmicin was shown to be significantly less toxic than ofloxacin. This finding is particularly relevant in deciding the optimal antibiotic to be applied in clinical situations in which the epithelium is absent or compromised, as after photorefractive keratectomy, alkali burns, or ulcerative keratitis.

In Vivo Toxicity of Netilmicin and Ofloxacin on Intact and Mechanically Damaged Eyes of Rabbit

PURPOSE

To evaluate the in vivo toxicity of netilmicin and ofloxacin using both normal and mechanically damaged eyes of rabbit.

METHODS

Male albino New Zealand rabbits were given either 0.3% netilmicin, 0.3% ofloxacin, or 0.9% sodium chloride solution by topical instillation (50 microL) into the conjunctival sac 6 times daily for 5 days. In some animals a 6-mm-diameter epithelial wound was mechanically made to the center of the cornea. Ocular toxicity on normal eyes was evaluated by impression cytology of the conjunctiva, histology of the entire globes, and scanning electron microscopy (SEM) of the cornea. Analysis of toxicity and reepithelialization on wounded corneas was evaluated by SEM with observations being made 48 and 72 hours after induction of the wound.

RESULTS

Cytologic, histopathologic, and SEM analyses of normal healthy eyes following netilmicin treatment revealed no signs of toxicity, whereas those treated with ofloxacin revealed alterations in the cornea (stromal swelling) and conjunctiva (infiltration of polymorphonuclear cells) with reduced goblet cell numbers. Wounded corneas treated with netilmicin exhibited normal morphology and reepithelialization, whereas the administration of ofloxacin resulted in disordered cellular organisation and slower rates of epithelial recovery.

CONCLUSIONS

Netilmicin, an antibacterial aminoglycoside, is well tolerated even in an experimental wound-healing model where the integrity of the ocular surface is compromised, whereas ofloxacin, a fluoroquinolone, appears to provoke an inflammatory response in the normal eye and a clear alteration of reepithelialization in the wounded eye. These findings suggest that netilmicin may offer a superior toxicological profile in both normal eyes and clinical situations where the integrity of the ocular epithelium is suspect.

Effect of ofloxacin and netilmicin on human corneal and conjunctival cells in vitro

The purpose of this study was to compare the cytotoxic effects of the fluoroquinolone ofloxacin with that of the aminoglycoside netilmicin. Human corneal epithelial cells (HCE-T) and human conjunctival epithelial cells (Wong-Kilbourne derivative of Chang conjunctiva) were exposed to antibiotics (0.08-5.0 mg/mL) for 4 or 24 hours. Cell proliferation and viability were assessed with the MTT assay, neutral red uptake, and bromo deoxy uridine incorporation. In both cell lines, ofloxacin inhibited cell proliferation and viability. These effects were time and dose dependent. Concentrations of ofloxacin ranging from 0.4 to 2.4 mg/mL (0.04% to 0.24%) produced a 50% inhibition of proliferation and viability. In contrast, netilmicin induced no toxic effect. The differences between ofloxacin and netilmicin were highly statistically significant (p < 0.001). This finding is particularly relevant in deciding the optimal antibiotic to be applied in clinical situations in which the epithelium is compromised.