Cyclopentenylcytosine (CPE-C): In Vitro and In Vivo Evaluation as an Antiviral against Adenoviral Ocular Infections.

Adenoviruses are the major cause of ocular viral infections worldwide. Currently, there is no approved antiviral treatment for these eye infections. Cyclopentenylcytosine (CPE-C) is an antiviral that has demonstrated activity against more than 20 viruses. The goals of the current study were to determine the in vitro and in vivo antiviral activity of CPE-C as well as its ocular toxicity. Antiviral activity was evaluated in vitro using standard plaque reduction assays to determine the 50% effective concentrations (EC50s) and in vivo in the Ad5/NZW rabbit ocular replication model. Ocular toxicity was determined in uninfected rabbit eyes following topical ocular application. The in vitro EC50s for CPE-C ranged from 0.03 to 0.059 µg/mL for nine adenovirus types that commonly infect the eye. Ocular toxicity testing determined CPE-C to be non-irritating or practically non-irritating by Draize scoring. In vivo, 3% CPE-C topically administered 4X or 2X daily for 7 days to adenovirus-infected eyes demonstrated effective antiviral activity compared with the negative control and comparable antiviral activity to the positive control, 0.5% cidofovir, topically administered twice daily for 7 days. We conclude CPE-C was relatively non-toxic to rabbit eyes and demonstrated potent anti-adenoviral activity in vitro and in vivo.

The Rcs Stress Response System Regulator GumB Modulates Serratia marcescens-Induced Inflammation and Bacterial Proliferation in a Rabbit Keratitis Model and Cytotoxicity In Vitro.

In this study, we tested the hypothesis that the conserved bacterial IgaA-family protein, GumB, mediates microbial pathogenesis associated with Serratia marcescens ocular infections through regulation of the Rcs stress response system. The role of the Rcs system and bacterial stress response systems for microbial keratitis is not known, and the role of IgaA proteins in mammalian pathogenesis models has only been tested with partial-function allele variants of Salmonella. Here, we observed that an Rcs-activated gumB mutant had a >50-fold reduction in proliferation compared to the wild type within rabbit corneas at 48 h and demonstrated a notable reduction in inflammation based on inflammatory signs, including the absence of hypopyons, and proinflammatory markers measured at the RNA and protein levels. The gumB mutant phenotypes could be complemented by wild-type gumB on a plasmid. We observed that bacteria with an inactivated Rcs stress response system induced high levels of ocular inflammation and restored corneal virulence to the gumB mutant. The high virulence of the ΔrcsB mutant was dependent upon the ShlA cytolysin transporter ShlB. Similar results were found for testing the cytotoxic effects of wild-type and mutant bacteria on a human corneal epithelial cell line in vitro. Together, these data indicate that GumB regulates virulence factor production through the Rcs system, and this overall stress response system is a key mediator of a bacterium's ability to induce vision-threatening keratitis.

Topical Astodrimer Sodium, a Non-Toxic Polyanionic Dendrimer, Demonstrates Antiviral Activity in an Experimental Ocular Adenovirus Infection Model.

There is no approved antiviral therapy for adenovirus (HAdV) ocular infections. Astodrimer sodium (SPL7013) is a polyanionic dendrimer with antiviral activity. The current study evaluated the ocular tolerability and anti-adenoviral efficacy of topical SPL7013 in rabbit ocular models. In a tolerability study, rabbits were treated with 3% SPL7013, vehicle, or 0.5% cidofovir. Their eyes were graded using the Draize scale. In antiviral efficacy studies, HAdV5 inoculated eyes were treated with 3% SPL7013, vehicle, or 0.5% cidofovir. Eyes were cultured for the virus on days 0, 1, 3, 4, 5, 7, 9, 11, and 14. Viral titers were determined. There were no differences in Draize scores between 3% SPL7013 and vehicle on any day. Cidofovir produced significantly higher Draize scores on day 12 than SPL7013 and vehicle. The 3% SPL7013 and 0.5% cidofovir significantly reduced daily viral titers and positive cultures per total compared with vehicle on several different days. The 3% SPL7013 and 0.5% cidofovir significantly reduced the duration of HAdV5 shedding compared to vehicle. The 3% SPL7013 demonstrated significantly more antiviral activity compared with vehicle in the Ad5/NZW rabbit ocular model. The 3% SPL7013 induced "minimal" to "practically non-irritating" Draize scores in the ocular tolerability study. Further development of astodrimer sodium as a topical antiviral therapy for adenoviral ocular infections is indicated.

In Vitro Evaluation of a Hypochlorous Acid Hygiene Solution on Established Biofilms.

OBJECTIVES: The purpose of this study was to determine whether a commercial formulation of hypochlorous acid hygiene solution (0.01%), Avenova, can destroy existing biofilms formed by ocular clinical bacterial isolates, including blepharitis isolates of Staphylococcus aureus and coagulase-negative staphylococci, and a keratitis isolate of Pseudomonas aeruginosa. METHODS: Biofilms grown in bacterial growth media on disposable contact lens cases were challenged with hypochlorous acid hygiene solution. At various time points, surviving bacteria were quantified by serial dilution and colony counts. Staphylococcus aureus biofilms formed on glass were challenged using a hypochlorous acid hygiene solution and imaged using vital staining and confocal laser scanning microscopy. RESULTS: Bactericidal activity (≥3 Log10; 99.9%) was observed for all tested bacterial species after a 30-min exposure. Staphylococcus aureus biofilms had a bactericidal level of killing by 10 min (P<0.01), Staphylococcus capitis by 5 min (P<0.001), Staphylococcus epidermidis by 30 min (P<0.001), and P. aeruginosa by 10 min (P<0.01). Confocal microscopy and crystal violet staining analysis of bacterial biofilms treated with hypochlorous acid solution both demonstrated that biofilm bacteria were readily killed, but biofilm structure was largely maintained. CONCLUSIONS: Hypochlorous acid (0.01%) hygiene solution was able to achieve bactericidal levels of killing of bacteria in biofilms but did not disrupt biofilm structures. Susceptibility of tested staphylococcal blepharitis isolates varied by species, with S. capitis being the most susceptible and S. epidermidis being the least susceptible.

Cefiderocol Is an Effective Topical Monotherapy for Experimental Extensively Drug-Resistant Pseudomonas aeruginosa Keratitis.

Purpose: To test cefiderocol, a siderophore-cephalosporin antibiotic for topical monotherapy treatment of experimental extensively drug-resistant (XDR) Pseudomonas aeruginosa keratitis. Design: Preclinical study. Subjects and Controls: Deidentified P. aeruginosa keratitis isolates, XDR P. aeruginosa from eye drop outbreak, rabbits, saline, cefiderocol 50 mg/ml, ciprofloxacin 0.3%, and tobramycin 14 mg/ml. Methods Intervention or Testing: Cefiderocol antibacterial activity against P. aeruginosa keratitis isolates (n = 135) was evaluated by minimum inhibitory concentration (MIC) testing. Ocular toxicity/tolerability and antibacterial efficacy were tested in vivo with experimental rabbit models. Corneal concentrations and stability were assessed using a bioassay. Main Outcome Measures: Minimum inhibitory concentration analysis for susceptibility, graded tests for ocular toxicity/tolerability, colony-forming unit (CFU) analysis for bacterial burden, corneal cefiderocol concentrations. Results: One hundred percent of P. aeruginosa keratitis isolates were susceptible to cefiderocol (n = 135), the MIC90 was 0.125 µg/ml including the XDR isolate (MIC = 0.125 µg/ml). Topical cefiderocol 50 mg/ml was minimally toxic to the ocular surface and was well tolerated. For the XDR P. aeruginosa isolate, topical cefiderocol 50 mg/ml, significantly decreased corneal CFU compared with ciprofloxacin 0.3%, tobramycin 14 mg/ml, and saline. In addition, tobramycin 14 mg/ml was more effective than the saline control. Mean cefiderocol corneal concentrations were 191× greater than the MIC90 of the P. aeruginosa keratitis isolates. Refrigerated cefiderocol maintained antimicrobial activity over a 1-month period. Conclusions: These results demonstrate that cefiderocol is well tolerated on rabbit corneas and is effective against P. aeruginosa keratitis isolates in vitro and was effective in vivo against an XDR isolate in a rabbit keratitis model. Given the recent outbreak of keratitis caused by this XDR P. aeruginosa, cefiderocol is a promising additional antibiotic that should be further evaluated for topical treatment of keratitis caused by antibiotic resistant P. aeruginosa. Financial Disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Cefiderocol is an effective topical monotherapy for experimental extensively-drug resistant Pseudomonas aeruginosa keratitis.

Purpose: To test cefiderocol, a siderophore-cephalosporin antibiotic for topical monotherapy treatment of experimental extensively drug resistant (XDR) Pseudomonas aeruginosa keratitis. Design: Preclinical study. Subjects and Controls: Deidentified P. aeruginosa keratitis isolates, XDR P. aeruginosa from eye drop outbreak, rabbits, saline, cefiderocol 50 mg/ml, ciprofloxacin 0.3%, and tobramycin 14 mg/ml. Methods Intervention or Testing: Cefiderocol antibacterial activity against P. aeruginosa keratitis isolates (n=135) was evaluated by minimum inhibitory concentration (MIC) testing. Ocular toxicity/tolerability and antibacterial efficacy were tested in vivo with experimental rabbit models. Corneal concentrations and stability were assessed using a bioassay. Main Outcome Measures: MIC analysis for susceptibility, graded tests for ocular toxicity/tolerability, CFU analysis for bacterial burden, corneal cefiderocol concentrations. Results: 100% of P. aeruginosa keratitis isolates were susceptible to cefiderocol (n=135), the MIC90 was 0.125 µg/ml including the XDR isolate (MIC = 0.125 µg/ml). Topical cefiderocol 50 mg/ml was minimally toxic to the ocular surface and was well tolerated. For the XDR P. aeruginosa isolate, topical cefiderocol 50 mg/ml, significantly decreased corneal CFU compared to ciprofloxacin 0.3%, tobramycin 14 mg/ml, and saline. In addition, tobramycin 14 mg/ml was more effective than the saline control. Mean cefiderocol corneal concentrations were 191x greater than the MIC90 of the P. aeruginosa keratitis isolates. Refrigerated cefiderocol maintained antimicrobial activity over a one-month period. Conclusions: These results demonstrate that cefiderocol is well tolerated on rabbit corneas and is effective against P. aeruginosa keratitis isolates in vitro and was effective in vivo against an XDR isolate in a rabbit keratitis model. Given the recent outbreak of keratitis caused by this XDR P. aeruginosa, cefiderocol is a promising additional antibiotic that should be further evaluated for topical treatment of keratitis caused by antibiotic resistant P. aeruginosa.

Bacterial Keratitis: Similar Bacterial and Clinical Outcomes in Female versus Male New Zealand White Rabbits Infected with Serratia marcescens.

PURPOSE: Females and males respond differently to a number of systemic viral infections. Differences between females and males with respect to the severity of keratitis caused by Gram-negative bacteria such as Serratia marcescens are less well established. METHODS: In this study, we injected female and male New Zealand White rabbit corneas with a keratitis isolate of S. marcescens and evaluated the eyes after 48 hours for a number of clinical and microbiological parameters. RESULTS: No statistical differences in bacterial burden and corneal scores were recorded between female and male rabbits although there was a non-significant trend toward a higher frequency of female rabbits demonstrating hypopyons. CONCLUSIONS: This data suggests that for experimental bacterial keratitis studies involving Gram-negative rods, a single sex or mixed group of rabbit is sufficient for evaluating pathology and bacterial burdens. This will reduce the number of animals used for subsequent studies.

Ranpirnase (OKG-0301), a Novel Ribonuclease, Demonstrates Antiviral Activity against Adenovirus in the Ad5/NZW Rabbit Ocular Replication Model.

Adenovirus ocular infections are common ocular viral infections seen worldwide, for which there is no approved antiviral therapy available. Ranpirnase is a novel ribonuclease which preferentially degrades tRNA resulting in an inhibition of protein synthesis. The study goal was to determine the anti-adenoviral activity of topical formulations of ranpirnase (OKG-0301) on adenoviral replication in the Ad5/NZW rabbit ocular replication model. NZW rabbits were inoculated in both eyes with human adenovirus type 5 (HAdV5) after corneal scarification. A day later, topical therapy was initiated in both eyes with 0.03% OKG-0301, 0.003% OKG-0301, saline or 0.5% cidofovir. Eyes were cultured to determine HAdV5 eye titers over 2 weeks. OKG-0301 (0.03% and 0.003%) and 0.5% cidofovir decreased viral titers compared to saline. Furthermore, both OKG-0301 formulations and 0.5% cidofovir shortened the duration of the HAdV5 infection compared to saline. Both 0.03% OKG-0301 and 0.003% OKG-0301 demonstrated increased antiviral activity compared to saline in the Ad5/NZW rabbit ocular replication model. The antiviral activity of the OKG-0301 groups was similar to that of the positive antiviral control, 0.5% cidofovir. Ranpirnase (OKG-0301) may be a potential candidate for a topical antiviral for adenoviral eye infections. Further clinical development is warranted.

Reactive silver inks for antiviral, repellent medical textiles with ultrasonic bleach washing durability compared to silver nanoparticles.

Medical textiles are subject to particularly harsh disinfection procedures in healthcare settings where exposure risks are high. This work demonstrates a fabric treatment consisting of a reactive silver ink and low surface energy PDMS polymer that provides for superhydrophobicity and antiviral properties against enveloped herpes simplex virus stocks even after extended ultrasonic bleach washing. The antiviral properties of reactive silver ink has not been previously reported or compared with silver nanoparticles. The fabric treatment exhibits high static contact angles and low contact angle hysteresis with water, even after 300 minutes of ultrasonic bleach washing. Similarly, after this bleach washing treatment, the fabric treatment shows reductions of infectious virus quantities by about 2 logs compared to controls for enveloped viruses. The use of silver ink provides for better antiviral efficacy and durability compared to silver nanoparticles due to the use of reactive ionic silver, which demonstrates more conformal coverage of fabric microfibers and better adhesion. This study provides insights for improving the wash durability of antiviral silver fabric treatments and demonstrates a bleach wash durable, repellent antiviral treatment for reusable, functional personal protective equipment applications.

The in vitro Evaluation of the Activity of COVID-19 Antiviral Drugs Against Adenovirus.

PURPOSE: Presently, there is no approved antiviral therapy for adenovirus (HAdV) ocular infections. During the COVID-19 pandemic, increased attention has been focused on antiviral treatments. Remdesivir, hydroxychloroquine, ivermectin, and umifenovir (Arbidol) have been touted as potential antiviral treatments for COVID-19. The goal of the current study was to determine whether these potential COVID-19 antivirals produce in vitro antiviral activity against a panel of ocular adenovirus types. METHODS: The 50% effective concentrations (EC50) of remdesivir (REM), hydroxychloroquine (HCQ), ivermectin (IVM), umifenovir (UMF) and cidofovir (CDV) (positive antiviral control) were determined for the human HAdV types HAdV3, HAdV4, HAdV5, HAdV7a, HAdV8, HAdV19/64 and HAdV37 using standard plaque-reduction assays in A549 cells. RESULTS: The range of mean in vitro EC50 concentrations for each antiviral across the range of HAdV types is as follows: The positive antiviral control, CDV, ranged from 0.47 to 9.62 µM; REM ranged from 0.21 to 11.27 µM; UMF ranged from 3.72 to 64.8 µM; IVR ranged from 2.60 to 201.3 µM; and HCQ was >10 µM for all Ad types because of toxicity to the A549 cells. REM produced lower EC50 concentrations than CDV for 6 of 7 HAdV types. Potency increases with lower EC50 concentrations. CONCLUSION: REM demonstrated anti-adenovirus activity in a range similar to that demonstrated by cidofovir. UMF and IVR demonstrated larger ranges of antiviral activity than CDV and REM across the panel of HAdV types. The anti-adenovirus activity of HCQ could not be determined due to cytotoxicity. Further investigation of REM, UMF, and IVR as antivirals for adenovirus is indicated.

Filociclovir Is an Active Antiviral Agent against Ocular Adenovirus Isolates In Vitro and in the Ad5/NZW Rabbit Ocular Model.

Presently, there is no FDA- or EMA-approved antiviral for the treatment of human adenovirus (HAdV) ocular infections. This study determined the antiviral activity of filociclovir (FCV) against ocular HAdV isolates in vitro and in the Ad5/NZW rabbit ocular model. The 50% effective concentrations (EC50) of FCV and cidofovir (CDV) were determined for several ocular HAdV types using standard plaque reduction assays. Rabbits were topically inoculated in both eyes with HAdV5. On day 1, the rabbits were divided into four topical treatment groups: (1) 0.5% FCV 4x/day × 10 d; (2) 0.1% FCV 4x/day × 10 d; (3) 0.5% CDV 2x/day × 7 d; (4) vehicle 4x/day × 10 d. Eyes were cultured for virus on days 0, 1, 3, 4, 5, 7, 9, 11, and 14. The resulting viral eye titers were determined using standard plaque assays. The mean in vitro EC50 for FCV against tested HAdV types ranged from 0.50 to 4.68 µM, whereas those treated with CDV ranged from 0.49 to 30.3 µM. In vivo, compared to vehicle, 0.5% FCV, 0.1% FCV, and 0.5% CDV produced lower eye titers, fewer numbers of positive eye cultures, and shorter durations of eye infection. FCV demonstrated anti-adenovirus activity in vitro and in vivo.

Topical Vancomycin 5% Is More Efficacious Than 2.5% and 1.25% for Reducing Viable Methicillin-Resistant Staphylococcus aureus in Infectious Keratitis.

PURPOSE: Topical vancomycin 5% (50 mg/mL) has been used for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) keratitis, but patient comfort has many clinicians using lower concentrations. We compared the efficacy of different concentrations of vancomycin in the treatment of experimental MRSA keratitis. METHODS: The corneas of 45 rabbits were infected with 2000 colony-forming units (CFUs) of MRSA. Corneal epithelium was abraded in the left eyes to mimic corneal ulceration. After 4 hours, the corneal CFUs were determined at the onset of treatment. The remaining rabbits were divided into 4 treatment groups (n = 9): 1) vancomycin 5%, 2) vancomycin 2.5%, 3) vancomycin 1.25%, and 4) saline. The rabbits were treated topically in both eyes every 15 minutes for 5 hours. One hour after treatment, the rabbits were clinically examined and euthanized, corneas were removed, and CFUs were determined to analyze vancomycin penetration, treatment efficacy, and bactericidal effect. RESULTS: Ocular toxicity was concentration dependent from mild to moderate. For the abraded corneas, the CFUs of the vancomycin 5% group were lower than 2.5% and 1.25%, and all vancomycin groups were lower than saline. The CFUs of 2.5% were lower but similar to 1.25%. The vancomycin 5% group demonstrated a bactericidal effect and the best penetration. The CFUs of the abraded corneas treated with saline were lower than those of the intact corneas, indicating a possible antibacterial effect from the ocular surface. CONCLUSIONS: Vancomycin 5% was most potent for treating experimental MRSA keratitis. The clinician may need to reassess treatment regarding antibacterial efficacy and patient comfort.

The In Vitro Evaluation of Povidone-Iodine Against Multiple Ocular Adenoviral Types.

PURPOSE: Povidone-iodine (P-I) is being touted as a topical antiviral treatment for eye infections caused by adenovirus (Ad). This study evaluated the in vitro antiviral activity of the several P-I concentrations previously used in clinical studies against multiple ocular Ad types commonly associated with eye infections. METHODS: The antiviral activity of four concentrations of P-I was compared to vehicle for seven types of Ad after incubating the P-I with Ad at 33°C for various lengths of time. Following incubation and neutralization of the P-I with sodium thiosulfate, viral titers were determined for each Ad type and time point. RESULTS: Virucidal (99.9%, ≥3-Log10) reductions in titers were produced for 5%, 2%, and 0.4% P-I at 1 min for types Ad5 and Ad7a. Similar reductions were produced at 5 min for types Ad3, Ad4, and Ad8. For type Ad19/64, virucidal reductions took 60 min for 5% P-I and 15 min for 2% and 0.4%. For type Ad37, 60 min (5%), 15 min (2%), and 5 min (0.4%) were required to produce virucidal reductions. There were no virucidal reductions in titers produced by 0.001% P-I. CONCLUSIONS: P-I produced greater than 3-Log10 reductions of titers at 1-5 min for most of the ocular types tested (types Ad3, Ad4, Ad5, Ad7a, and Ad8). However, it took longer (15-60 min) for these reductions to be produced for types Ad19/64 and Ad37. The antiviral activity of P-I may be Ad type dependent.

Benzalkonium Chloride Demonstrates Concentration-Dependent Antiviral Activity Against Adenovirus In Vitro.

Purpose: Adenoviral conjunctivitis is the most common cause of conjunctivitis worldwide with no approved antiviral treatment. Benzalkonium chloride (BAK) is a common preservative in ophthalmic medications and is the active ingredient in some skin disinfectants and hand sanitizers. BAK is known to be effective in killing bacteria and enveloped viruses; however, its activity against ocular types of nonenveloped adenoviruses (Ads) is unknown. The goal was to determine whether BAK is an effective antiviral agent against common human ocular types of adenovirus in vitro. Methods: The direct inactivating activity of BAK was determined by incubating several human adenovirus types with BAK concentrations of 0.001%, 0.003%, 0.005%, 0.01%, 0.1%, and 0% for 1 h at 33°C. Resulting adenovirus titers were determined after treatment. Decreases in titers of ≥3 Log10 were considered virucidal, while decreases in titers of <1 Log10 were considered ineffective. Results: BAK 0.1% was virucidal for Ad3, Ad5, Ad7a, Ad19/64, and Ad37, while it reduced titers >1 Log10, but <3 Log10 for Ad4 and Ad8. Decreases in titers >1 Log10 were demonstrated for BAK 0.003%, 0.005%, and 0.01% for Ad5 only. Decreases in titers for the other adenovirus types for those concentrations were ≤0.53 Log10. 0.001% BAK produced minimal decreases in titers for all types. Conclusions: BAK, at 0.01% or less was not consistently effective as an antiviral against adenovirus, but higher concentrations, such as 0.1%, should be further investigated as a possible topical treatment for adenoviral ocular infections, providing ocular toxicity is not an issue.

Topical 0.5% moxifloxacin prevents endophthalmitis in an intravitreal injection rabbit model.

INTRODUCTION: Intravitreal injections for the treatment of retinal disease have increased the risk of endophthalmitis. We developed a rabbit model to investigate whether topical 0.5% moxifloxacin could prevent endophthalmitis after an intravitreal injection. METHODS: A rabbit model of intravitreal injection to produce endophthalmitis was developed by injecting triamcinolone into the vitreous through a depot of subconjunctival Staphylococcus aureus (10(7) cfu). Endophthalmitis was evaluated clinically and confirmed by culture. The model was tested with a commercially available brand of topical 0.5% moxifloxacin (N = 10) and saline (N = 10). In brief, after bacterial subconjunctival challenge, a topical treatment was administered every 15 min for 1 h. Immediately thereafter, triamcinolone was injected into the vitreous through the treated bacterial depot. Topical 0.5% moxifloxacin and saline were administered QID over the next 72 h. All rabbits were examined daily, euthanized, and tested for viable bacteria when clinical signs of endophthalmitis were observed. RESULTS: Anti-infective treatment with topical 0.5% moxifloxacin prevented the development of endophthalmitis (0/9 rabbits), compared to topical saline (6/10 rabbits; P = 0.01; power = 0.99). CONCLUSIONS: Topical 0.5% moxifloxacin provided effective prophylaxis to prevent endophthalmitis after an intravitreal injection of triamcinolone. This unique model may prove valuable to demonstrate prophylaxis for other anti-infectives at an intravitreal injection site.

Zymar (Gatifloxacin 0.3%) shows excellent Gram-negative activity against Serratia marcescens and Pseudomonas aeruginosa in a New Zealand White rabbit keratitis model.

PURPOSE: Whereas gatifloxacin, a newer fluoroquinolone, was engineered to increase its Gram-positive potency, we assessed whether it still retained significant Gram-negative activity in vivo. Specifically, we compared the efficacy of Zymar (gatifloxacin 0.3%), Ciloxan (ciprofloxacin 0.3%), and fortified tobramycin (14 mg/mL) in the treatment of experimental Gram-negative bacterial infections of Serratia marcescens (SM) and Pseudomonas aeruginosa (PA) in the New Zealand White (NZW) rabbit keratitis model. METHODS: A total of 30 NZW rabbits each were intrastromally inoculated in both eyes with approximately 1000 CFU of SM and PA. By E-test, the minimum inhibitory concentrations (MICs; microg/mL) for SM were gatifloxacin (0.125), ciprofloxacin (0.047), and tobramycin (1.5), and for PA were gatifloxacin (0.125), ciprofloxacin (0.19), and tobramycin (0.5). After 16 hours, the rabbits were divided into 4 treatment groups: (1) Zymar, (2) Ciloxan, (3) fortified tobramycin, and (4) saline control. One drop was instilled in both eyes every 15 minutes for 5 doses and then every 30 minutes for 14 doses. One hour after the final treatment, the animals were euthanized, and bacterial colony counts from the corneas were determined. RESULTS: For SM, Zymar and Ciloxan significantly reduced (P < 0.001, ANOVA) the colony counts compared with tobramycin and saline control. Zymar was more effective than Ciloxan (P < 0.001, ANOVA). For PA, all antibiotics reduced equivalently the colony counts compared with the saline control (P = 0.005, ANOVA). CONCLUSIONS: The enhanced Gram-positive activity of gatifloxacin is not associated with any decreased Gram-negative activity in vivo. Zymar may prove useful for SM and PA keratitis.

N-chlorotaurine is an effective antiviral agent against adenovirus in vitro and in the Ad5/NZW rabbit ocular model.

PURPOSE: To determine whether N-chlorotaurine (NCT) demonstrates antiviral activity against adenovirus (Ad) in vitro and in the Ad5/NZW rabbit ocular model. METHODS: The in vitro activity of NCT was evaluated by incubating different Ad serotypes with several concentrations of NCT for 1 hour and determining the reduction in Ad titers. In rabbit study 1, Ad5-infected eyes were treated with 2.5%, 2.0%, and 1.0% NCT; 0.5% cidofovir; or saline. NCT and saline groups were treated 10 times for 1 day and then 5 times daily for 6 days. In rabbit study 2, Ad5-infected eyes were treated with 1.0% NCT/0.1% ammonium chloride (NH4Cl), 0.1% NCT/1.0% NH4Cl, 0.1% NCT/0.1% NH4Cl, and 0.5% cidofovir or saline. The NCT and saline groups were treated five times daily for 10 days. Cidofovir-treated eyes received the authors' standard cidofovir dose regimen: twice daily for 7 days. RESULTS: In vitro, NCT demonstrated concentration-dependent direct inactivation of all ocular Ad serotypes tested. Rabbit study 1: 2.5%, 2.0%, 1.0% NCT, and cidofovir demonstrated significantly fewer positive cultures per total cultures during days 1 to 14, compared with saline. Rabbit study 2: 1.0% NCT/0.1% NH4Cl, 0.1% NCT/1.0% NH4Cl, 0.1% NCT/0.1% NH4Cl, and cidofovir demonstrated significantly fewer positive cultures per total cultures, during days 1 to 14; shorter durations of shedding; and lower mean combined titers, during days 7 to 14, compared with saline. Cidofovir was significantly more effective than NCT in several outcome measures in both rabbit studies. CONCLUSIONS: NCT demonstrated antiviral activity against adenovirus in vitro and in vivo. Further development of NCT as a topical antimicrobial is indicated.

Role of topical fluoroquinolones on the pathogenesis of diffuse lamellar keratitis in experimental in vivo studies.

PURPOSE: To investigate the potential role of commercially available topical fluoroquinolones in diffuse lamellar keratitis (DLK) using New Zealand White rabbit models. SETTING: Campbell Ophthalmic Microbiology Laboratory at the University of Pittsburgh, Pittsburgh, Pennsylvania, USA. METHODS: In a DLK challenge model, laser in situ keratomileusis flaps were created by a microkeratome in rabbit eyes (n = 10 per group) and the stromal beds were treated with 1 drop of Ciloxan (ciprofloxacin 0.3%), Ocuflox (ofloxacin 0.3%), balanced salt solution (BSS), or Pseudomonas aeruginosa endotoxin before flap closure. After the procedure, eyes were treated with the same drugs 4 times daily. On postoperative day 1, the eyes were examined by slitlamp and graded (modified Linebarger DLK grading scale) in a masked fashion. In a DLK exacerbation model, all eyes received 1 drop of endotoxin on the stromal interface followed by flap closure. After the procedure, the rabbit eyes (10 per group) were treated 4 times daily with Ciloxan, Ocuflox, or BSS and graded for DLK on postoperative day 1 as before. RESULTS: In the challenge model, Ciloxan, Ocuflox, and endotoxin all produced higher median DLK scores than the BSS control (P = .02). Ciloxan produced significant DLK in more eyes and had higher median scores (70%, 1.0) than Ocuflox (40%, 0.5) or endotoxin (45%, 0.5) (P = .05). In the endotoxin-induced model, Ciloxan produced significantly higher DLK scores than Ocuflox or BSS (P = .05). CONCLUSIONS: Topical fluoroquinolones caused and exacerbated DLK in rabbit models. Ocuflox was associated with less DLK than Ciloxan. The clinical significance of these findings can only be assessed in clinical trials.

An Independent Evaluation of a Novel Peptide Mimetic, Brilacidin (PMX30063), for Ocular Anti-infective.

OBJECTIVE: Brilacidin (BRI), a novel defensin mimetic, was evaluated as an ocular anti-infective. METHODS: In vitro: Potency based on MIC90s was compared for 50 Staphylococcus aureus (SA), 50 Staphylococcus epidermidis (SE), and 25 each of Streptococcus pneumonia (SP), Streptococcus viridans (SV), Moraxella (MS), Haemophilus influenzae (HI), Pseudomonas aeruginosa (PA), and Serratia marcescens (SM). In vivo: Using established methods, ocular toxicity was graded with Draize testing. For efficacy testing, both corneas of 24 rabbits were infected with methicillin-resistant S. aureus (MRSA), whereas the corneal epithelium was removed in the left eye. After 4 h, 21 topical drops over 5 h were administered to 4 groups: BRI 0.5%, vancomycin (VAN) 5%, saline, and no treatment. The eyes were clinically graded and the corneas were harvested for colony counts. RESULTS: In vitro: Both SA and SE had the lowest minimum inhibitory concentrations among the bacterial groups. The MIC90s to BRI for SP, SV, MS, HI, PA, and SM were 4, 32, 256, 32, 16, and 128-fold higher, respectively, than SA and SE. In vivo: Draize testing determined BRI 0.5% to be minimally irritating. For abraded corneas, BRI was not statistically different from VAN for reducing MRSA. BRI was bactericidal. For intact corneas, VAN reduced more CFU than BRI. BRI reduced CFU in abraded corneas more than intact corneas suggesting poor corneal penetration. CONCLUSIONS: BRI has Gram-positive in vitro activity; topical BRI 0.5% was minimally irritating; and BRI 0.5% was equally efficacious as VAN in a MRSA keratitis model when the corneal epithelium was removed.

The In Vitro Evaluation of Tigecycline and the In Vivo Evaluation of RPX-978 (0.5% Tigecycline) as an Ocular Antibiotic.

PURPOSE: The goals of the current study were to determine the in vitro antibacterial activity of tigecycline against multiple clinically relevant ocular pathogens and to evaluate the in vivo ocular tolerability and efficacy of 0.5% tigecycline in a methicillin-resistant Staphylococcus aureus (MRSA) keratitis model. METHODS: In vitro: Minimum inhibitory concentrations (MICs) were determined for 110 clinical conjunctivitis isolates, 26 keratitis isolates of Pseudomonas aeruginosa, and 10 endophthalmitis isolates each of MRSA, methicillin-susceptible S. aureus (MSSA), MR, and MS coagulase-negative Staphylococcus. TOLERABILITY: Six uninfected rabbits were topically treated in both eyes with 0.5% tigecycline, vehicle, or saline every 15 min for 3 h. EFFICACY: Thirty-two rabbits were intrastromally injected with 700 Colony Forming Units (CFU) of MRSA in both eyes and were separated into 4 groups (n = 8): tigecycline 0.5%; vancomycin 5%; saline; and no treatment (euthanized before treatment for baseline CFU). Four hours after MRSA challenge, topical treatment of 1 drop every 15 min for 5 h was initiated. One hour after treatment, the corneas were harvested for CFU. The data were analyzed nonparametrically. RESULTS: In vitro: Tigecycline demonstrated lower MICs than the other tested antibiotics against gram-positive organisms, especially MRSA, while MICs against gram-negative pathogens, including fluoroquinolone-resistant P. aeruginosa, appeared to be in the treatable range with aggressive topical therapy. TOLERABILITY: 0.5% tigecycline was graded as minimally irritating. EFFICACY: 0.5% tigecycline and vancomycin produced similar reductions in CFU and were less than saline (P < 0.05). Tigecycline and vancomycin demonstrated 99.9% reductions compared with baseline CFU. CONCLUSIONS: Tigecycline is a potential candidate for a topical ocular antibiotic.