Comparative In Vitro Activity of Levofloxacin, Ofloxacin, and Ciprofloxacin Against Ocular Streptococcal Isolates

A Literature-Based Review and Analysis of the Pharmacodynamics of the Dose Frequency of Topical 0.3% Ciprofloxacin and 0.3% Ofloxacin in the Day-1 Treatment of Bacterial Keratitis

Purpose: To determine the appropriate dose frequency for the second-generation fluoroquinolones (2FQs), ciprofloxacin 0.3% and ofloxacin 0.3%, in the day-1 treatment of bacterial keratitis (BK) based on the corneal concentrations achievable and required Minimum Inhibitory Concentration₉₀ (MIC₉₀) of common BK isolates. Methods: Literature-based ocular MIC₉₀ required to treat bacterial isolates of BK patients were determined for each fluoroquinolone. Published corneal concentrations for each 2FQ, and the drop regimens used to reach these concentrations, were then analyzed to determine the relationship between the corneal 2FQ concentration and the amount of drug applied per hour and the total amount applied. Results: Significant relationships were found to exist for corneal concentrations of both ciprofloxacin and ofloxacin and the amount of drug applied per hour (both P = 0.005), and the total amount of drug applied (P = 0.003 and P = 0.0004, respectively). Derived ciprofloxacin drops/hour corneal concentrations agreed well with both a literature-based regimen and the manufacturers' day-1 drop regimen for various MIC₉₀. Derived ofloxacin drops per hour indicated a higher rate than that suggested by the manufacturer. Conclusions: Both a literature-based and the manufacturers' drop regimens for the day-1 treatment of BK using 0.3% ciprofloxacin have a pharmacodynamic basis, which is related to the required MIC₉₀ of commonly encountered isolates in BK. Dose frequency for 0.3% ofloxacin should be in line with the manufacturers' maximum suggested drop regimen. Commonly suggested drop regimens below these recommendations for either FQ may need to be revised in view of these findings.

Isolation of Streptococcus cuniculi from corneal lesion in laboratory-raised mice

Corneal lesions appearing as white mass beneath intact epithelium, with ocular discharge in one mouse, was observed in a batch of laboratory-raised BALB/c mice (n=9 of 56). The affected mice remained active, well-groomed and had normal appetite. Isolates recovered from swab cultures of the external and internal contents of the eye had partial 16S rRNA gene sequence of 99.1% similarity to Streptococcus cuniculi. No previous report of S. cuniculi infection in laboratory rodents has been presented. The isolate was susceptible to all antibiotics tested. We suggest S. cuniculi is an opportunistic bacteria in laboratory mice but are uncertain of its source. Our findings revealed that S. cuniculi is able to colonize laboratory mice and should be considered when mice present with eye lesion or ocular discharge.

Rose Bengal Photodynamic Antimicrobial Therapy for Patients With Progressive Infectious Keratitis: A Pilot Clinical Study

PURPOSE

To report clinical outcomes of rose bengal photodynamic antimicrobial therapy (RB-PDAT) as an adjunct treatment for severe, progressive infectious keratitis.

DESIGN

Consecutive interventional case series.

METHODS

Patients with progressive infectious keratitis unresponsive to standard medical therapy underwent RB-PDAT at the Bascom Palmer Eye Institute from January 2016 through March 2018. RB-PDAT was performed by applying a solution of rose bengal (0.1% or 0.2% RB in balanced salt solution) to the de-epithelialized cornea for 30 minutes, followed by irradiation with a 6 mW/cm² custom-made green LED source for 15 minutes (5.4 J/cm²).

RESULTS

The current study included 18 patients (7 male and 11 female) ranging from 17 to 83 years old. Acanthamoeba was the most frequent microbe (10/17; 59%), followed by Fusarium spp. (4/17; 24%), Pseudomonas aeruginosa (2/17; 12%), and Curvularia spp. (1/17; 6%); 1 patient had no confirmed microbiologic diagnosis. Main clinical risk factor for keratitis included contact lens wear (79%). The average area of epithelial defect prior to first RB-PDAT was 32 ± 27 mm² and average stromal depth hyperreflectivity measured with anterior segment optical coherence tomography was 269 ± 75 μm. Successful RB-PDAT (avoidance of therapeutic keratoplasty) was achieved in 72% of the cases, with an average time to clinical resolution (decreased pain and inflammation with re-epithelialization and infiltrate resolution) of 46.9 ± 26.4 days after RB-PDAT. Time of follow-up after RB-PDAT was 13.3 ± 5.7 months.

CONCLUSION

RB-PDAT can be considered as an adjunct therapy for cases of severe, progressive infectious keratitis before performing a therapeutic keratoplasty.

A Review of New Fluoroquinolones : Focus on their Use in Respiratory Tract Infections

The new respiratory fluoroquinolones (gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, and on the horizon, garenoxacin) offer many improved qualities over older agents such as ciprofloxacin. These include retaining excellent activity against Gram-negative bacilli, with improved Gram-positive activity (including Streptococcus pneumoniae and Staphylococcus aureus). In addition, gatifloxacin, moxifloxacin and garenoxacin all demonstrate increased anaerobic activity (including activity against Bacteroides fragilis). The new fluoroquinolones possess greater bioavailability and longer serum half-lives compared with ciprofloxacin. The new fluoroquinolones allow for once-daily administration, which may improve patient adherence. The high bioavailability allows for rapid step down from intravenous administration to oral therapy, minimizing unnecessary hospitalization, which may decrease costs and improve quality of life of patients. Clinical trials involving the treatment of community-acquired respiratory infections (acute exacerbations of chronic bronchitis, acute sinusitis, and community-acquired pneumonia) demonstrate high bacterial eradication rates and clinical cure rates. In the treatment of community-acquired respiratory tract infections, the various new fluoroquinolones appear to be comparable to each other, but may be more effective than macrolide or cephalosporin-based regimens. However, additional data are required before it can be emphatically stated that the new fluoroquinolones as a class are responsible for better outcomes than comparators in community-acquired respiratory infections. Gemifloxacin (except for higher rates of hypersensitivity), levofloxacin, and moxifloxacin have relatively mild adverse effects that are more or less comparable to ciprofloxacin. In our opinion, gatifloxacin should not be used, due to glucose alterations which may be serious. Although all new fluoroquinolones react with metal ion-containing drugs (antacids), other drug interactions are relatively mild compared with ciprofloxacin. The new fluoroquinolones gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin have much to offer in terms of bacterial eradication, including activity against resistant respiratory pathogens such as penicillin-resistant, macrolide-resistant, and multidrug-resistant S. pneumoniae. However, ciprofloxacin-resistant organisms, including ciprofloxacin-resistant S. pneumoniae, are becoming more prevalent, thus prudent use must be exercised when prescribing these valuable agents.

Corneal inlay implantation complicated by infectious keratitis

BACKGROUND/AIMS

To report five cases of infectious keratitis following corneal inlay implantation for the surgical correction of presbyopia.

METHODS

This was a retrospective, observational case series. Five eyes of five patients were identified consecutively in two emergency departments during a 1-year period, from November 2013 to November 2014. Patients' demographics, clinical features, treatment and outcomes are described.

RESULTS

There were four female patients and one male, aged 52-64 years. Three patients had the KAMRA inlay (AcuFocus) and two had the Flexivue Microlens inlay (Presbia Coöperatief U.A.) inserted for the treatment of presbyopia and they presented from 6 days to 4 months postoperatively. Presenting uncorrected vision ranged from 6/38 to counting fingers. One patient's corneal scrapings were positive for a putatively causative organism, Corynebacterium pseudodiphtheriticum, and all patients responded to broad-spectrum fortified topical antibiotics. All patients lost vision with final uncorrected visual acuity ranging from 6/12 to 6/60 and best-corrected vision ranging from 6/7.5 to 6/12. Two patients' corneal inlays were explanted and three remained in situ at last follow-up.

CONCLUSIONS

Infectious keratitis can occur at an early or late stage following corneal inlay implantation. Final visual acuity can be limited by stromal scarring; in the cases where the infiltrate was small and off the visual axis at the time of presentation, the final visual acuity was better than those patients who presented with larger lesions affecting the visual axis. Though infection may necessitate removal of the inlay, early positive response to treatment may enable the inlay to be left in situ.

Review of moxifloxacin hydrochloride ophthalmic solution in the treatment of bacterial eye infections

Moxifloxacin hydrochloride ophthalmic solution 0.5% (Vigamox((R))) is the ocular formulation/adaptation of moxifloxacin. Moxifloxacin is a broad spectrum 8-methoxyfluoroquinolone which terminates bacterial growth by binding to DNA gyrase (topoisomerase II) and topoisomerase IV, essential bacterial enzymes involved in the replication, translation, repair and recombination of deoxyribonucleic acid. Affinity for both enzymes improves potency and reduces the probability of selecting resistant bacterial subpopulations. Vigamox is a bactericidal, concentration dependent, anti-infective. It is preservative free, and well tolerated with minimal ocular side effects. It provides increased penetration into ocular tissues and fluids with improved activity against Streptococci and Staphylococci species and moderate to excellent activity against clinically relevant, gram-negative ocular pathogens.

Retinal Toxicity of Intraocular Vancomycin and Ceftazidime in Vitrectomized Rabbit Eyes

The purpose of this study was to evaluate the retinal toxicity of vancomycin and ceftazidime combined into an infusion solution that was intraoculary given after or during vitrectomy. Forty albino rabbits were divided into 4 groups of 10 each. Vitrectomized right eyes of groups 1, 2, and 3 were given recommended doses of vancomycin and ceftazidime alone or combined, while right eyes in the fourth group were vitrectomized using an infusion solution to which was added ceftazidime and vancomycin combination. Toxicity was tested with electroretinography (ERG) and light microscopy. ERG and light microscopy did not show any toxicity signs associated with vancomycin or ceftazidime alone or with combined therapy. Vancomycin and/or ceftazidime can reliably and effectively be used combined in an infusion solution at recommended doses after and during vitrectomy. This treatment modality does not have any toxic effects to retinal structures and is an alternative method to separate injections of the two antimicrobial agents.

Review of third-and fourth-generation fluoroquinolones in ophthalmology: in-vitro and in-vivo efficacy

INTRODUCTION

Beginning with second-generation ciprofloxacin 0.3% and ofloxacin 0.3%, fluoroquinolones have been widely used in the treatment and prophylaxis of ocular infections. However, their in-vitro potencies have been decreasing steadily since their introduction. Third-generation levofloxacin 0.5% produces higher ocular tissue penetration, thereby reducing the risk of selecting for decreased fluoroquinolone potency. Fourth-generation gatifloxacin 0.3% and moxifloxacin 0.5% have structural modifications that both reduce risk of resistance and improve potency against Gram-positive bacteria. A new third-generation formulation, levofloxacin 1.5%, was recently introduced, demonstrating increased ocular penetration compared with gatifloxacin 0.3% but clinical equivalence to its second-generation parent, ofloxacin 0.3%, in two randomized trials.

METHODS

We investigated the therapeutic potential of levofloxacin 1.5% and compared it to that of existing fourth-generation fluoroquinolones. A MEDLINE search was conducted using the following search terms: moxifloxacin or gatifloxacin; levofloxacin; minimum inhibitory concentration or prevention or prophylaxis; keratitis or endophthalmitis.

RESULTS

Nine eligible studies published between 2002 and 2008 were identified, eight of which are presented. The five in-vitro studies demonstrated that moxifloxacin and gatifloxacin are statistically more potent than levofloxacin against Gram-positive organisms and similar in potency in most cases of Gram-negative bacteria. In-vivo animal models testing moxifloxacin or gatifloxacin against levofloxacin 0.5% (no clinical trials testing the efficacy of levofloxacin 1.5% have yet been published) demonstrated that fourth-generation agents were superior to third-generation levofloxacin 0.5% for prophylaxis of Gram-positive bacteria-induced infections and were equal to, or better than, levofloxacin 0.5% for the treatment of Gram-negative infections.

CONCLUSION

Fourth-generation agents have increased potency against Gram-positive bacteria compared with levofloxacin, while maintaining similar potency against Gram-negative bacteria. Although levofloxacin 1.5% has demonstrated superior ocular penetration relative to gatifloxacin, the limited available data do not suggest this translates into superior clinical activity compared with moxifloxacin, which has significantly greater ocular penetration and better Gram-positive potency than gatifloxacin.

Ocular TRUST: nationwide antimicrobial susceptibility patterns in ocular isolates

PURPOSE

Ocular Tracking Resistance in U.S. Today (TRUST) annually evaluates in vitro antimicrobial susceptibility of Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae to ciprofloxacin, gatifloxacin, levofloxacin, moxifloxacin, penicillin, azithromycin, tobramycin, trimethoprim, and polymyxin B in national samples of ocular isolates.

DESIGN

Laboratory investigation.

METHODS

Prospectively collected ocular isolates (197 S. aureus, 49 S. pneumoniae, and 32 H. influenzae) from 35 institutions and archived ocular isolates (760 S. pneumoniae and 356 H. influenzae) from 34 institutions were tested by an independent, central laboratory. Mean minimum inhibitory concentrations that would inhibit growth of 90% of the tested isolates (MIC(90)) were interpreted as susceptible, intermediate, or resistant according to standardized breakpoints for systemic treatment. S. aureus isolates were classified as methicillin susceptible (MSSA) or methicillin resistant (MRSA).

RESULTS

MSSA or MRSA susceptibility patterns were virtually identical for the fluoroquinolones, that is, MSSA susceptibility was 79.9% to 81.1% and MRSA susceptibility was 15.2%. Trimethoprim was the only agent tested with high activity against MRSA. All S. pneumoniae isolates were susceptible to gatifloxacin, levofloxacin, and moxifloxacin; 89.8% were susceptible to ciprofloxacin. H. influenzae isolates were 100% susceptible to all tested agents but trimethoprim. Ocular TRUST 1 data were consistent with the eight-year longitudinal sample of archived ocular isolates.

CONCLUSIONS

The fluoroquinolones were consistently active in MSSA, S. pneumoniae, and H. influenzae. After more than a decade of intensive ciprofloxacin and levofloxacin use as systemic therapy, 100% of ocular S. pneumoniae isolates were susceptible to gatifloxacin, levofloxacin, and moxifloxacin; nonsusceptibility to ciprofloxacin was less than 15%. High-level in vitro MRSA resistance suggests the need to consider alternative therapy to fluoroquinolones when MRSA is a likely pathogen.