Comparison of corneal and aqueous humor penetration of moxifloxacin, gatifloxacin and levofloxacin during keratoplasty

Incremental effect of topical and oral moxifloxacin administration with surgical intracameral prophylaxis

OBJECTIVE

To determine how supplemental perioperative topical or oral moxifloxacin administration impacts anterior chamber (AC) antibiotic concentrations beyond those achieved by intracameral (IC) administration alone for postoperative endophthalmitis (POE) prophylaxis.

DESIGN

Mathematical modeling.

METHODS

The mathematical model developed by Arshinoff, Modabber, and Felfeli was adapted to calculate all reported data. A literature review of pharmacokinetic data for topical and oral moxifloxacin was used to inform the expansion of the model.

RESULTS

Our previously constructed IC model yields a dose of moxifloxacin in the AC sufficient to confer bactericidal coverage against the most common POE pathogen, methicillin-sensitive Staphylococcus aureus (MSSA), for ∼40 hours postoperatively. Topical 0.5% moxifloxacin eye drops alone, administered every 4 or 6 hours, achieve an AC concentration just above or at the mutant prevention concentration (MPC) for MSSA, respectively, whereas 8-hour dosing produces levels generally below the MPC. Combining topical moxifloxacin with IC increases the AC concentration above IC alone only after 20 or more hours and maintains the AC concentration at, or just below, the MPC for MSSA for as long as the drops are continued. Combined perioperative oral moxifloxacin with IC increases AC levels over IC alone only after 16 hours and maintains the AC concentration above the MPC for MSSA for an additional 5 hours, owing to the systemic reservoir.

CONCLUSIONS

The addition of topical or oral moxifloxacin supplemental to IC can extend the duration of bactericidal coverage for the most common, but not the most resistant POE-causing pathogens.

Ultrasound-assisted gatifloxacin delivery in mouse cornea, in vivo

Gatifloxacin is a 4th generation fluoroquinolone antibiotic used in the clinic to treat ocular infection. One limitation of gatifloxacin is its relatively poor corneal penetration, and the increase of its trans-corneal delivery would be beneficial to reduce the amount or frequency of daily dose. In this study, ultrasound treatment was applied to enhance the trans-corneal delivery of gatifloxacin without damage. Experiments were conducted on mouse eyes in ex vivo and in vivo conditions. Ultrasound waves with 1 MHz in frequency, 1.3 W/cm² in intensity were applied onto the mouse cornea for 5 minutes, and then gatifloxacin ophthalmic solution was instilled and left there for 10 minutes. 3D gatifloxacin distribution in the cornea was measured by two-photon microscopy (TPM) imaging based on its intrinsic fluorescence. Longitudinal TPM imaging of ultrasound treated mouse corneas showed the increase of initial gatifloxacin intensities on the corneal surface compared to untreated mouse corneas by 67%, and then the increased gatifloxacin delivery into the cornea from the surface at later time. The delivered gatifloxacin in the corneal epithelium stayed longer in the ultrasound treated corneas than in the untreated corneas. The enhanced trans-corneal delivery and extended stay of gatifloxacin in the mouse cornea by ultrasound treatment could be beneficial for therapeutic effects. This study demonstrated the detail process of enhanced trans-corneal gatifloxacin delivery by ultrasound treatment.

Gatifloxacin inducing apoptosis of stromal fibroblasts through cross-talk between caspase-dependent extrinsic and intrinsic pathways

AIM

To reveal the cytotoxicity and related mechanisms of gatifloxacin (GFX) to stromal fibroblasts (SFs) in vitro.

METHODS

SFs were treated with GFX at different concentrations (0.009375%-0.3%), and their viability was detected by MTT method. The cell morphology was observed using light/transmission electron microscope. The plasma membrane permeability was measured by AO/EB double-staining. Then cell cycle, phosphatidylserine (PS) externalization, and mitochondrial transmembrane potential (MTP) were analyzed by flow cytometry. DNA damage was analyzed by electrophoresis and immunostaining. ELISA was used to evaluate the caspase-3/-8/-9 activation. Finally, Western blotting was applied for detecting the expressions of apoptosis-related proteins.

RESULTS

Morphological changes and reduced viability of GFX-treated SFs demonstrated that GFX above 0.009375% had cytotoxicity to SFs with dependence of concentration and time. GFX-treating cells also showed G₁ phase arrest, increased membrane permeability, PS externalization and DNA damage, which indicated that GFX induced apoptosis of SFs. Additionally, GFX could activate the caspase-8, caspase-9, and caspase-3, induce MTP disruption, downregulate B-cell leukemia-2 (Bcl-2) and B-cell leukemia-XL (Bcl-XL), and upregulate Bcl-2 assaciated X protein (Bax), Bcl-2-associated death promoter (Bad), Bcl-2 interacting domain (Bid) and cytoplasmic cytochrome C in SFs, suggesting that caspase-dependent extrinsic and intrinsic pathways were related to GFX-contributed apoptosis of SFs.

CONCLUSION

The cytotoxicity of GFX induces apoptosis of SFs through triggering the caspase-dependent extrinsic and intrinsic pathways.

Comparative Study Between Topical Gatifloxacin 0.5% and Moxifloxacin 0.5% as a Prophylactic Measure Before Intraocular Surgery

Purpose: To compare equal concentrations (0.5%) of moxifloxacin and gatifloxacin ophthalmic solutions with regard to conjunctival bacterial reduction as well as anterior chamber penetration. Methods: One hundred patients were divided into 2 groups. Group A received moxifloxacin 0.5% ophthalmic solution and group B received gatifloxacin 0.5% ophthalmic solution 4 times a day for 3 days before surgery and 5 times with 30 min intervals on the day of surgery. Two conjunctival swabs were obtained: one before instillation of antibiotic and the second 30 min after instillation of the last antibiotic drop. Specimens were sent for culture and susceptibility testing. At the time of surgery, 0.1 mL of aqueous fluid was aspired, and aqueous concentration of fluoroquinolones was identified using reverse-phase high-pressure liquid chromatography assay technique. Results: The most common flora isolated was coagulase-negative Staphylococcus (32.9%), followed by Staphylococcus aureus (24.8%) and Corynebacterium diphtheria (19.1%). Moxifloxacin aqueous concentration was higher compared with gatifloxacin [1.75 ± 0.98 standard deviation (SD) and 0.75 ± 0.22 SD, respectively]. This 2.3-fold difference in aqueous humor antibiotic concentrations was statistically significant (P ≤ 0.001). There was significant difference between the means of conjunctival colony-forming unit after antibiotic administration in both the study groups (2.17 ± 1.54 SD in group A and 1.56 ± 1.09 SD in group B). Conclusions: Moxifloxacin 0.5% was found to penetrate anterior chamber more than gatifloxacin 0.5%, enforcing its use for prophylaxis before intraocular surgeries. However, gatifloxacin 0.5% eye drops were able to reduce conjunctival bacterial load, more supporting its use before extraocular and refractive surgeries.

Comparative activity of antimicrobials against Pseudomonas aeruginosa, Achromobacter xylosoxidans and Stenotrophomonas maltophilia keratitis isolates

BACKGROUND/AIMS

Achromobacter xylosoxidans and Stenotrophomonas maltophilia are emerging corneal pathogens, which are closely related to Pseudomonas aeruginosa, and have intrinsic resistance to many commonly available antimicrobials. The purpose of this study is to compare the in vitro efficacy of 12 antimicrobial agents against A. xylosoxidans, S. maltophilia and P. aeruginosa isolates recovered from clinical cases of keratitis.

METHODS

Recovered corneal isolates (n=58) were identified and extracted from the Microbiology Data Bank of the Bascom Palmer Eye Institute. Comparative in vitro minimum inhibitory concentration (MIC) susceptibility profiles for fluoroquinolones, aminoglycosides, beta-lactams and miscellaneous antibiotics were recorded using the E-test methodology. Pharmacodynamic indices (Cmax/MIC) were calculated.

RESULTS

A. xylosoxidans and S. maltophilia isolates were resistant to fluoroquinolones, aminoglycosides and ceftazidime (susceptibility rate ranging from 0% to 30%) while P. aeruginosa isolates showed a susceptibility rate of 95%-100% to these antimicrobials (P<0.00001 for the various antimicrobials). Exception was moxifloxacin with 80% of susceptibility rate to S. maltophilia isolates and Cmax/MIC=10.19. Ninety to 100% susceptibility rates were found for minocycline and trimethoprim/sulfamethoxazole for both A. xylosoxidans and S. maltophilia. One hundred per cent of the A. xylosoxidans isolates were susceptible to piperacillin/tazobactam and ticarcillin/clavulanic acid.

CONCLUSIONS

There is a significant difference in susceptibility patterns between A. xylosoxidans, S. maltophilia and P. aeruginosa. Fluoroquinolones and aminoglycosides may not be effective against A. xylosoxidans and S. maltophilia. Antibiotics that are not commercially available as eye drops, such as beta-lactams for A. xylosoxidans, and trimethoprim/sulfamethoxazole and minocycline for both A. xylosoxidans and S. maltophilia should be considered.

Clinical utility of antimicrobial susceptibility measurement plate covering formulated concentrations of various ophthalmic antimicrobial drugs

PURPOSE

The purpose of this study was to evaluate the clinical utility of SG17, an ophthalmic antimicrobial susceptibility measurement plate.

DESIGN

This was a multicenter, retrospective, observational study.

PATIENTS AND METHODS

Using clinical isolates from patients with ocular infections, drug susceptibility testing using the Clinical Laboratory and Standards Institute standards was routinely conducted at five facilities. The minimum inhibitory concentrations of the isolated strains were determined using SG17 at the Research Foundation for Microbial Diseases of Osaka University. The records of antimicrobial drugs used and the therapeutic course were evaluated for all cases. The susceptibility results from SG17 and routine methods used at each facility were compared.

RESULTS

A total of 112 bacterial strains were isolated from 92 patients. Of these cases, keratitis was the most common (52.2%), followed by conjunctivitis (21.7%) and others (26.1%). Principal signs and symptoms resolved in all patients, indicating that therapeutic effects had been achieved. With SG17, drug susceptibility was determined in 98.9% of isolates compared with 30.4% of isolates determined using conventional methods. By adapting the Clinical Laboratory and Standards Institute standards to SG17 results, we found that 91.3% of patients were susceptible and 7.6% were resistant. In five patients, drugs with a resistant evaluation were initially administered with no effect, and the patients were then switched to drugs with a susceptible evaluation with final resolution, indicating agreement of clinical results with SG17.

CONCLUSION

SG17 can be used to determine drug susceptibility to antimicrobial agents currently used in ophthalmic practice. SG17 is useful for selecting antimicrobial drugs.

Safety of prophylactic intracameral moxifloxacin ophthalmic solution after cataract surgery in patients with penetrating keratoplasty

AIM

To determine the safety of prophylactic intracameral moxifloxacin after cataract surgery in patients with penetrating keratoplasty (PKP).

METHODS

In this retrospective study of consecutive patients who had phacoemulsification cataract surgery after PKP, were treated with intracameral moxifloxacin 0.5% ophthalmic solution (0.5 mg/0.1 mL). The main outcome measures were anterior chamber reaction, best corrected visual acuity (BCVA), corneal endothelial cell count (ECC), and central corneal thickness (CCT).

RESULTS

Fifty-five patients were recruited (26 males, 29 females). The mean age was 54.36±4.97y (range 45-64y). All eyes had improved postoperative BCVA. The mean BCVA was 0.25 preoperatively and 0.57 postoperatively, which was statistically significant (P<0.001). One eye had 3+, 7 eyes had 2+, 12 eyes had 1+ and 8 eyes had trace amount of aqueous cells on the first day after surgery. All eyes had no anterior chamber cells at subsequent follow up examinations. Effective phacoemulsification time was 4.33±1.01s. The mean ECC was 2340.20 cells/mm(2) preoperatively and 1948.75 cells/mm(2) 1mo postoperatively (P<0.001). The increase of 21.09 µm in postoperative pachymetry 1mo after surgery was statistically significant (P<0.001).

CONCLUSION

No untoward effects were observed after intracameral injection of moxifloxacin (0.5 mg/0.1 mL) in terms of anterior chamber reaction, CCT, ECC, and visual rehabilitation at the conclusion of cataract surgery in patients with PKP.

Preparation and characterization of molecularly imprinted poly(hydroxyethyl methacrylate) microspheres for sustained release of gatifloxacin

Molecularly imprinted poly(hydroxyethyl methacrylate) microspheres (PHEMA MIPMs) were prepared via precipitation polymerization in this article, using gatifloxacin (GFLX), hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethacrylate (EGDMA) as template molecule, functional monomer and cross-linker, respectively. The effects of reaction medium, initial total monomers, cross-linker and molecular imprinting on the polymerization were investigated systematically. The interaction between GFLX and HEMA in pre-solution was studied by UV-Visible spectrophotometer, both size and morphology of products were characterized by a scanning electron microscope. When the total initial monomer concentration was 1 vol%, EGDMA content was 70 mol%, a group of uniform PHEMA MIPMs were prepared at different GFLX/MAA molar ratios, with diameter range from 2.06 ± 0.07 to 2.82 ± 0.20 μm. The results of drug loading and in vitro release experiments demonstrated that PHEMA MIPMs could achieve a higher GFLX loading content and a more acceptable sustained release than non-imprinted ones.

Antimicrobial Agents in Ophthalmology

Many types of antimicrobial agents have been introduced for the treatment of ocular infectious diseases. Some ocular infections have been eradicated such as smallpox, while others have been controlled by public health measures such as trachoma. The resilience of viruses and the tenacity of bacteria have led to the evolution of old diseases and the emergence of new infections. Continuous search for new antimicrobial agents for the treatment of infectious diseases is, therefore, highly desirable.

New infectious agents are discovering the human race, and the ecological changes are exposing mankind to new viruses and bacteria. In addition, air travel and disruption of geographic barriers are leading to new forms of infectious diseases.

In the twentieth century, there was a widespread false optimism that infectious diseases are eradicated by antimicrobial agents. It was soon discovered that many infections require new strategies for the treatment of ocular infections.

The new antimicrobial agents that have been introduced over the past century can be classified into four major categories including (1) antibiotics that inhibit cell wall synthesis and integrity, (2) antibiotics that inhibit and suppress cell membrane functions, (3) antibiotics that interfere the protein synthesis, and (4) antibiotics that modulate nucleic acid synthesis.

The selection of antimicrobial agents for the treatment of ocular infectious diseases is based on the most frequently encountered organisms, the pharmacokinetics of the antibiotics, the dosage required, the ocular penetration, and the cost of therapy. The stumbling blocks to safe and effective antimicrobial therapy in ocular infections include the resistance of the microorganisms, toxicity of the drug, and poor ocular penetration of antimicrobial agents.

Methicillin-Resistant Staphylococcus aureus Keratitis after Descemet's Stripping Automated Endothelial Keratoplasty

Purpose

We report a case of methicillin-resistant Staphylococcus aureus (MRSA) keratitis after Descemet's stripping automated endothelial keratoplasty (DSAEK).

Case Report

An 87-year-old woman who had undergone a DSAEK 4 months previously was referred to Tokushima University Hospital with a diagnosis of infectious keratitis after DSAEK. A white abscess and infiltration in the inferior cornea of the right eye were observed. We started an empiric therapy using topical levofloxacin and chloramphenicol on the basis of the microscopic findings of the corneal scraping concurrently with cultivation of the cornea.

Results

A strain of MRSA was isolated from the corneal sample. Although the strain was susceptible to chloramphenicol, it was resistant to quinolone. The keratitis improved rapidly due to empiric therapy, and topical steroids could be resumed 6 days after initiation of the empiric therapy.

Conclusions

To our knowledge, this is the first case of MRSA keratitis, and the second case of bacterial keratitis, after DSAEK. MRSA keratitis can occur following uneventful DSAEK. The empiric therapy on the basis of results from a light microscopic examination of a Gram-stained corneal scraping and restarting topical steroids in the early stages of medication contributed to the good clinical course of this case.