A Novel and Low-cost Approach for Intravitreal Injection in an Experimental Model of Endophthalmitis

Abstract

Purpose: Animal models are necessary in understanding the pathogenesis of endophthalmitis and are also necessary to assist the development of new therapeutics for this sight-threatening ocular inflammation. Hamilton syringes are usually preferred to inject pathogens when performing experiments on test subjects, however, this method has technical and financial disadvantages. In this study, we report the findings and assess the related benefits of applying a novel low-cost intravitreal injection technique to initiate endophthalmitis in a mouse model while using the Eppendorf tip and a 26G needle.
 Methods: The 18-hr culture of clinical isolates of bacteria (Staphylococcus aureus and Pseudomonas aeruginosa) and fungus (Aspergillus flavus and Candida albicans) were resuspended to a final concentration of 10,000 colony forming units (CFU)/1 µL which were separately injected intravitreally into C57BL/6 mice (6–8 weeks) using a 0.1–2.5µL pipette attached to the modified Eppendorf tip with a 26G needle. The contralateral eye served as vehicle/uninjected control. Disease progression was determined by assessing the corneal haze, opacity, bacterial burden, and retinal histology of the eyes used in the model. Following euthanization, bacteria-infected mice were enucleated after 24 hr of the initial injection, and fungus-infected mice after 72 hr.
 Results: Of the 50 mice injected, the modified technique was successful in 48 mice. Two mice were excluded due to cataract formed by accidental injury to the lens. The experimental endophthalmitis mice model successfully mimicked the natural clinical course. Clinical assessment and histopathology confirmed the influx of inflammatory cells into the posterior segment of the eye along with dissolution of retinal architecture.
 Conclusion: Our novel method of injection using a modified Eppendorf tip and 26G needle yielded a cost-effective mouse model of clinical endophthalmitis, resulting in reproducible infection for understanding various aspects of its pathobiology.

Global Transcriptomic Profiling of Innate and Adaptive Immunity During Aspergillus flavus Endophthalmitis in a Murine Model

“…The A. flavus endophthalmitis mice model was developed as reported previously. 31 Briefly, C57BL/6 mice were anesthetized by administering ketamine (35 mg/Kg) and xylazine (5 mg/Kg) along with topical anesthetic (0.5% proparacaine hydrochloride). Eyes were wiped clean with a topical antiseptic 10% betadine (Win-Medicare Pvt Ltd), and the pupils were dilated with 1% tropicamide (Ophtha Pharma) to allow visualization of the injected needle inside the eye.…”

“…Eyes were wiped clean with a topical antiseptic 10% betadine (Win-Medicare Pvt Ltd), and the pupils were dilated with 1% tropicamide (Ophtha Pharma) to allow visualization of the injected needle inside the eye. Then, 1 μL of fungal spore suspension containing 15,000 spores were intravitreally injected into the mid vitreous using a modified needle injector 31 under a surgical microscope (ZEISS Stemi 508 Stereo Microscope; Zeiss, Jena, Germany). The contralateral eye was injected with sterile 1 × PBS which served as the control.…”