Efficacy of ciprofloxacin and dexamethasone in experimental pseudomonas endophthalmitis

OculusGraphy: Signal Analysis of the Electroretinogram in a Rabbit Model of Endophthalmitis Using Discrete and Continuous Wavelet Transforms

BACKGROUND

The electroretinogram is a clinical test used to assess the function of the photoreceptors and retinal circuits of various cells in the eye, with the recorded waveform being the result of the summated response of neural generators across the retina.

METHODS

The present investigation involved an analysis of the electroretinogram waveform in both the time and time-frequency domains through the utilization of the discrete wavelet transform and continuous wavelet transform techniques. The primary aim of this study was to monitor and evaluate the effects of treatment in a New Zealand rabbit model of endophthalmitis via electroretinogram waveform analysis and to compare these with normal human electroretinograms.

RESULTS

The wavelet scalograms were analyzed using various mother wavelets, including the Daubechies, Ricker, Wavelet Biorthogonal 3.1 (bior3.1), Morlet, Haar, and Gaussian wavelets. Distinctive variances were identified in the wavelet scalograms between rabbit and human electroretinograms. The wavelet scalograms in the rabbit model of endophthalmitis showed recovery with treatment in parallel with the time-domain features.

CONCLUSIONS

The study compared adult, child, and rabbit electroretinogram responses using DWT and CWT, finding that adult signals had higher power than child signals, and that rabbit signals showed differences in the a-wave and b-wave depending on the type of response tested, while the Haar wavelet was found to be superior in visualizing frequency components in electrophysiological signals for following the treatment of endophthalmitis and may give additional outcome measures for the management of retinal disease.

Visual outcomes of acute bacterial endophthalmitis treated with adjuvant intravitreal dexamethasone: A meta-analysis and systematic review

Adjunctive treatment of bacterial endophthalmitis with intravitreal steroids is a topic of controversy among many ophthalmologists. The objective of this study is to evaluate the effects of intravitreal dexamethasone on the visual outcomes of patients with acute bacterial endophthalmitis through a systematic review and meta-analysis. A literature search of PubMed, Scopus, and Cochrane Library databases was performed to include studies on the visual outcomes of adjuvant intravitreal dexamethasone in patients with acute bacterial endophthalmitis. The review is based on the Preferred Reporting Items for Systematic review and Meta-Analysis (PRISMA) protocol. A total of 1545 articles met our search criteria and after further review, two randomized controlled trials and three retrospective case series were included in the final analysis. A total of 126 eyes were treated with intravitreal dexamethasone combined with antibiotics, and another 139 eyes were treated with antibiotics alone. All cases of endophthalmitis were post-operative or post-intravitreal injection, with pooled results demonstrating no visual benefit with supplementation of intravitreal dexamethasone. Our meta-analysis does not show any visual benefit from steroid supplementation and yet, considering a relatively small number of patients included in each study, larger randomized controlled trials are required to further clarify the role of steroids in the treatment of acute bacterial endophthalmitis.

Modeling intraocular bacterial infections

Bacterial endophthalmitis is an infection and inflammation of the posterior segment of the eye which can result in significant loss of visual acuity. Even with prompt antibiotic, anti-inflammatory and surgical intervention, vision and even the eye itself may be lost. For the past century, experimental animal models have been used to examine various aspects of the pathogenesis and pathophysiology of bacterial endophthalmitis, to further the development of anti-inflammatory treatment strategies, and to evaluate the pharmacokinetics and efficacies of antibiotics. Experimental models allow independent control of many parameters of infection and facilitate systematic examination of infection outcomes. While no single animal model perfectly reproduces the human pathology of bacterial endophthalmitis, investigators have successfully used these models to understand the infectious process and the host response, and have provided new information regarding therapeutic options for the treatment of bacterial endophthalmitis. This review highlights experimental animal models of endophthalmitis and correlates this information with the clinical setting. The goal is to identify knowledge gaps that may be addressed in future experimental and clinical studies focused on improvements in the therapeutic preservation of vision during and after this disease.

Efficacy of Intravitreal Levofloxacin 0.5% Ophthalmic Solution in Treating Pseudomonas Aeruginosa Endophthalmitis on a Rabbit Model

PURPOSE

To evaluate the efficacy of intravitreal levofloxacin 0.5% ophthalmic solution as treatment of Pseudomonas aeruginosa endophthalmitis in a rabbit model.

DESIGN

This is a parallel randomized experimental study.

METHODS

Twenty-six New Zealand white rabbits were enrolled. P. aeruginosa was inoculated intravitreally on the right eyes of all rabbits, which were further categorized into 2 groups, the treatment group (Group A) receiving 0.1 mL intravitreal injection levofloxacin 0.5% 24 hours after inoculation and the control group (Group B), which had 0.1 mL intravitreal aqua destilata (placebo). Clinical observation of the eyes in each group was performed on the first until the sixth day after the inoculation using clinical grading scale. On the sixth day, the eyes were examined for microbiological and histopathologic evaluations.

RESULTS

The total clinical grading scores of each group were similar 24 hours after P. aeruginosa inoculation (P > 0.05). The total clinical grading scores of Group A on the sixth day and the difference in total clinical scores on the first and the sixth day were shown to be significantly lower than that of Group B (P < 0.05). Microbiological analysis revealed that there was a lower bacterial count in Group A (mean = 1.18 ± 0.93 logCFU/0.1 mL) compared with Group B (mean = 4.09 ± 1.51 logCFU/0.1 mL), and the histopathologic scores of both groups were also significantly different (P < 0.05).

CONCLUSIONS

Intravitreal levofloxacin 0.5% ophthalmic solution at 0.1 mL dose appeared to be effective in treating P. aeruginosa endophthalmitis in rabbits.

Adjunctive intravitreal dexamethasone in the treatment of acute endophthalmitis following cataract surgery

Purpose

Controversy exists regarding the use of intravitreal dexamethasone (IVD) as an anti-inflammatory adjunct to intravitreal antibiotics in patients with acute endophthalmitis following cataract surgery. The purpose of this project was to evaluate our experience regarding the effect of adjunctive IVD use on visual outcomes in such patients.

Design

Retrospective, comparative case series.

Methods

Study population: Patients treated for acute endophthalmitis following cataract surgery from 1995–2004. Intervention: In addition to standard intravitreal antibiotic treatment, some patients also received a single adjunctive injection of IVD. Primary outcome measures: Median visual acuity at last follow-up and percentage of patients achieving a ≥3-line improvement in visual acuity. Secondary outcome measures: Inflammatory index scoring, including amount of cell and flare, height of hypopyon, and presence of fibrin as a function of time after treatment.

Results

Twenty-six eyes were treated with and 38 eyes without adjunctive IVD. Median presenting visual acuity was Hand Motion in both groups. Median visual acuity at last follow-up measured 20/40 in the IVD group and 20/50 in the No-IVD group (p = 0.75). Seventy-three percent of patients in the IVD group and 82% of patients in the No-IVD group achieved a ≥3-line improvement in visual acuity (p = 0.42). No significant difference was detected between the IVD and No-IVD groups for any of the three measures of inflammation.

Conclusion

The use of IVD did not significantly improve the final median visual acuity, the chance of achieving a ≥3-line improvement in visual acuity, or the amount of intraocular inflammation. Based on these findings, and the possible detrimental effect of IVD on visual outcomes previously reported in the literature, the use of IVD does not appear to be warranted as a routine adjunctive treatment in postoperative endophthalmitis.

[Advantages of corticosteroids in managing acute bacterial postoperative endophthalmitis]

Most studies show a trend toward a beneficial or at least neutral effect of associating corticosteroids and antibiotics. However, caution must be taken, with various factors considered: the type, virulence, and size of the inoculum, and the treatment chosen. Early intravitreal administration of 400 microg of dexamethasone seems to be beneficial in treating postoperative Staphylococcus epidermidis-related endophthalmitis. However, a large-scale prospective, randomized, controlled study is mandatory to gain evidence supporting steroid therapy in postoperative endophthalmitis.

Toward improving therapeutic regimens for Bacillus endophthalmitis

PURPOSE

Bacillus cereus causes the most virulent and refractory form of endophthalmitis. The authors analyzed the effectiveness of early treatment with vancomycin or gatifloxacin, with or without dexamethasone, for experimental B. cereus endophthalmitis.

METHODS

Rabbit eyes were injected intravitreally with 100 colony-forming units of B. cereus. At 2, 4, or 6 hours after infection, eyes were injected intravitreally with 0.1 mL gatifloxacin (0.3%), vancomycin (1.0%), either antibiotic plus dexamethasone, dexamethasone alone (1.0%), or PBS. Eyes were analyzed by electroretinography, bacterial quantitation, and antibiotic penetration analysis. Drug toxicity toward Müller cells, retinal pigment epithelium, and cones was also analyzed.

RESULTS

Eyes treated at 2 hours with vancomycin or gatifloxacin, with or without dexamethasone, maintained higher ERG amplitudes than the dexamethasone alone and PBS control groups. Eyes treated with antibiotic plus dexamethasone at 6 hours had reduced retinal function compared to antibiotic treatment alone. With the exception of vancomycin with or without dexamethasone at 6 hours, all antibiotic treatments sterilized eyes. Only gatifloxacin reached aqueous concentrations greater than the minimal inhibitory concentration for B. cereus when measured at 8 hours. Neither gatifloxacin nor vancomycin was toxic to retinal cells in vitro.

CONCLUSIONS

Early intravitreal injection of vancomycin or gatifloxacin improved the therapeutic outcome of B. cereus endophthalmitis. The addition of dexamethasone to antibiotic treatment did not provide a therapeutic benefit over antibiotics alone and appeared to reduce the antibiotic efficacy of vancomycin 6 hours after infection. In this model, delay in treatment past 6 hours significantly reduced the potential for salvaging useful vision.

Endophthalmitis

Australia and New Zealand continue to be at the forefront of endophthalmitis research. In this Clinical Controversy, an ophthalmologist from each country presents different approaches to the management of a 72-year-old patient with routine endophthalmitis following cataract surgery. Mark Elder concludes that this case needs aqueous and vitreous aspirates for culture and the initial treatment of choice is intracameral vancomycin and amikacin. The evidence for intravitreal steroids is equivocal. Systemic antibiotics are indicated if there is a possibility of a bacterial biofilm present on the intraocular lens. Nigel Morlet concludes that timely intervention with appropriate antibiotics delivered in the right concentration to the vitreous cavity is the crux of successful management of endophthalmitis. Aggressive treatment of the inflammatory response is also required to further reduce the damage to the intraocular structures. Both ophthalmologists agree that vitrectomy is not necessarily the most appropriate treatment option.

Bacterial endophthalmitis: epidemiology, therapeutics, and bacterium-host interactions

Endophthalmitis is a severe inflammation of the interior of the eye caused by the introduction of contaminating microorganisms following trauma, surgery, or hematogenous spread from a distant infection site. Despite appropriate therapeutic intervention, bacterial endophthalmitis frequently results in visual loss, if not loss of the eye itself. Although the pathogenicity of bacterial endophthalmitis has historically been linked with toxin production during infection, a paucity of information exists as to the exact mechanisms of retinal toxicity and the triggers for induction of the intraocular immune response. Recently, research has begun to examine the bacterial and host molecular and cellular events that contribute to ocular damage during endophthalmitis. This review focuses on the causative agents and therapeutic challenges of bacterial endophthalmitis and provides current data from the analysis of the role of bacterial virulence factors and host inflammatory interactions in the pathogenesis of eye infections. Based on these and related studies, a hypothetical model for the molecular pathogenesis of bacterial endophthalmitis is proposed. Identifying and understanding the basic mechanisms of these bacterium-host interactions will provide the foundation for which novel, information-based therapeutic agents are developed in order to prevent vision loss during endophthalmitis.