Endophthalmitis was induced through intravitreal injection of Staphylococcus aureus in wild type (WT) C57BL/6 mice (n = 6) eyes (5000 CFU/eye) and in zebrafish (Danio rerio, AB strain) (n = 10) eyes (250,000 CFU/eye). PBS-injected eyes were used as a control. (A) A slit-lamp microscopy examination was performed on the eyes of both mice and zebrafish, and micrographs were taken for representative eyes at indicated time points. (B) For a histological analysis, eyes were enucleated at indicated time points and subjected to hematoxylin and eosin (H & E) staining for mice and Methylene Blue-Azure II for zebrafish eyes.

Endophthalmitis was induced by intravitreal injection of S. aureus in WT C57BL/6 mice (n = 6) eyes (5000 CFU/eye) and in zebrafish (n = 10) eyes (250,000 CFU/eye). PBS-injected eyes were used as a control. (A) A fundoscopic examination was performed on the eyes of both mice and zebrafish using Micron 3, and images were taken for representative eyes at indicated time points. (B) An angiography was performed through the injection of 2% fluorescent dye into the peritoneum of the mice and the caudal artery of the zebrafish using Micron 3.

Zebrafish eyes (n = 10) were infected with S. aureus (250,000 CFU/eye). At indicated time points, eyes were enucleated and homogenized, and the bacterial burden was estimated via serial dilution plating (* p < 0.05; ** p < 0.005; Student’s t-test).

Zebrafish eyes (n = 10) were infected with GFP-positive S. aureus (250,000 CFU/eye). At indicated time points, retinal cryosections were immunostained for GFP (green) and colabeled with TO-PRO 3 for nuclei (blue). S. aureus (shown by white arrows) was initially seen in choroidal and vitreous vasculature, with the remaining bacteria being cleared through the optic nerve head with time. INL: inner nuclear layer; GCL: ganglion cell layer; Vit: vitreous chamber; O/N: optic nerve; Ch: choroid; ROS: rod outer segment.

Zebrafish eyes (n = 10) were infected with GFP-positive S. aureus (250,000 CFU/eye). (A) Retinal cryosections were immunostained with anti-GFP antibody (green) and colabeled with TO-PRO 3 for nuclei (blue). S. aureus (as shown by black arrows) was located in the vitreous as well as in phagocytic cells. (B) Retinal sections were stained with Tetrazolium blue at indicated time points. The stained cells appeared to be macrophages with engulfed S. aureus in the vitreous cavity.

Zebrafish eyes (n = 10) were infected with S. aureus (250,000 CFU/eye) for 8 h. PBS-injected eyes were used as a control. Infected and control eyes were subjected to RNA isolation and qRT-PCR for Tnfα, Il-1β, and Il-6 cytokine genes. Data represent mean ± standard error of the mean (SEM); n = 3; ns, not significant; ** p < 0.01; *** p < 0.001; Student’s t-test.